The Megami Tensei series of games had its first launch September 11 of 1987 with Digital Devil Story: Megami Tensei, meaning it's slightly older than Final Fantasy!  This first game was a very loose adaptation of the light novel series Digital Devil Story.  It was a first person dungeon crawler with turn based combat, a trait every game in the series would retain until the late 90's early 2000's.  Notably, even this first game featured the ability to negotiate and recruit the demons and gods that make up most of the games' enemies, as well as the ability to fuse them into stronger entities.  Megami Tensei would go on to be one the Big Three Japanese RPG series alongside Final Fantasy and Dragon Quest.  However, unlike the other two series, very few of the games made it to North America (unsure about Europe) until after the 2000's.  This is probably because of the whole "negotiating and summoning demons" thing combined with the Abrahamic God being a frequent antagonist in the series.

Future installments through the rest of the 80's and 90's (including the first SHIN Megami Tensei) kept to the first's blueprint while adding things like multiple endings and the overarching themes of the series.  These themes include the eternal battle of Law and Chaos, the struggles of those caught in between to stay afloat (and often the rightness of finding the middle path), and the paradoxical strength and weakness of humans and humanism.  This is a series where solo runs are nearly impossible, where you must rely on your party to survive; however, your divine and demonic allies constantly manipulate you while your human friendships are strained or even break, normally violently and tragically.  Eventually, offshoots of the series took their own ideas in their own directions (the Persona series is a great example of this), but ATLUS kept making essentially the same games, seemingly unaffected by the flash and pomp much of the rest of the JRPG genre was embracing post FF7.

Then came SMT 3, what we knew here as SMT: Nocturne.  Nocturne broke with the first person view and sprites in favor of third person and 3D models (though still elegantly stylized, the game's art stands up to this day), but its more important break was the introduction of the press-turn system.  Every SMT game after Nocturne uses this system, even most of the spin-offs (including Persona) use some modification of it, and knowing how it works is essential to understanding combat in SMT. 

Here's the basics of the Press Turn System:

[*]The player and the enemy have separate sets of turns (a turn here = one action).  One side takes all of its turns, and then the other goes.
[*]Each side has a number of turns equal to the number of active party members in it.  Powerful enemies and sometimes the player are exceptions.
[*]Hitting an opponent's weakness or getting a critical hit transforms one of your turns into an "extra turn."

• Extra turns cannot become additional extra turns, so at most you can double your actions per turn this way.
  
• You can pass a turn from one party member to the next.  This gives an extra turn if you have none, but consumes an extra turn if you have any.
  

[*]Missing an attack (except ailments) or hitting an opponent with an attack they are immune to (including ailments) makes you lose two press turns.

• Hitting an absorb or reflect damage resistance makes you lose ALL of your turns, ending your round immediately.
  

[*] These rules apply to both you and the enemy. 

As such, the press turn system makes battles in SMT a game of momentum.  You want to consistently hit enemy weaknesses to gain turns, while having the opponent hit your resistances, miss, or be disabled by status ailments to lose theirs.  One bad party composition, tactical misstep, or risky gamble can kill the player even when fighting regular mobs, as all enemies can snowball the same way as the player given the chance.  Overly defensive play gives up the ability to gain additional turns, and strong HP and MP restoring items are very rare to put the player on a clock (can't keep healing forever).  However, the game is tuned such that, past the very beginning, the raw numbers of damage and HP are slanted against the player.  Offense is king in SMT, but healing and support skills are essential to buy the player the time they need to win.

SMT 4 plays much the same as Nocturne, with a few exceptions.  First off, unlike Nocturne (and many older SMT's) the game does not end when the protagonist dies.  The entire active party must be wiped out to lose. However, if you don't teach your demons one of two very rare skills you cannot summon or switch out party members while the protagonist is dead, putting you in tight spot nonetheless.  

Secondly, the protagonist does not learn skills from leveling up.  Rather, when a demon learns its final skill, you can choose to pass any of its known skills on to the player except for passive abilities (if the player character has no empty skill slots, you may replace an existing one).  Passing on a skill the protagonist already knows instead cheapens the MP cost for that skill when used by the protagonist.  

Third, the unique magatama system of Nocturne is replaced by equipped gear, handling stat bonuses and resistances.

Fourth, physical skills use MP in SMT 4/4A, whereas they consumed HP in Nocturne.

Fifth is that SMT 4 does away with random encounters, though on map encounter can ambush you or sometimes spawn directly under you.

Sixth is the app system, which is unique to the SMT 4 games and lets you customize your character in various ways.  The additional skill slot apps are sadly a near must buy which eat up a lot of app points, but beyond those there are a wide variety of choices to be made, from raising the level cap on demon fusion to apps which facilitate a diplomacy heavy play style.  There are even challenge mode apps, like bringing back the "instant game over if the protagonists dies" mechanic.

Seventh is the smirk status , which furthers the momentum based nature of the press turn system.  Whenever a character takes an action or has one performed on them that either gives their team press turns or takes them from the enemy, they have a chance to smirk.  The player or enemies may also gain smirk at the start of a fight if they score a blindside.  Smirking differs between 4 and 4:A, to prevent confusion I will only detail how it works in the latter.  

A smirking character has their weaknesses converted to normal resistances while smirking, their next hit is always a critical hit, actions with variable numerical effects always use the maximum values (like maximize spell in DnD), and some skills have additional effects when used while smirking.  Smirk is lost either two turns after it is gained or after the smirking character attacks, so it cannot be used to negate weaknesses forever.  A character cannot smirk when afflicted by a status ailment, and smirk is removed should a smirking character be inflicted with an ailment.  Some skills can forcibly grant or remove smirk with 100% odds. 

 To get anyone who cares up to speed, I am playing as Siddhartha (player chosen name, default is Nanashi), an androgynous youth living in apocalyptic Tokyo.  25 years ago some nasty experiments released all sorts of supernatural creatures into the world, which God took exception to and nuked the entire planet for.  Tokyo survived the nukes when its guardian deity Masakado turned into a giant stone dome, but that also trapped Tokyo underground with all the demons.  Siddhartha yearns to be a hunter and fight back against the gods and demons plaguing mankind, but gets horribly murdered at the start of the game before accomplishing much of anything.  A god named Dagda offers to return me to life if I'll be his Godslayer and generally do his bidding.  I accept, and with his boons grow in power and prestige as a hunter.

Along the way I accidentally release a bunch of world religion deities with an axe to grind against God, get the player character of the original SMT 4 kidnapped, learn that Dagda is not a people person, and proceed to kill every angel, demon, and god in my path.  Eventually I kill Dagda too, because I disagree with his stance on other people being allowed to exist (his opinion is that they shouldn't).  Though Tokyo is finally at peace, SMT's native Stephen Hawking expy informs me that God Himself is still out there and will never stop meddling in mankind's business (seeing as He believes it to be His business).  So I get all my friends, human and divine/demonic alike together, and we decide to go kill God like any self-respecting JRPG heroes.

Time to introduce our merry band.  Up first is Siddhartha, the protagonist.

Don't let the bars fool you, they only scale up to 200, but Siddhartha's magic is nearly 420  .  Also built with enough agility to always move first on my turn (more likely to act multiple times a turn as a result) and up my hit/evasion (since I use magic, which has high natural accuracy, I almost never miss esp. after buffs/debuffs).  Luck increases critical chance, makes me less likely to be crit, grants me a little ailment resistance, and tilts damage rolls in my favor slightly, among countless other small effects.  Strength and Dexterity only influence melee and gun attacks respectively, and so are dump stats for my magic inclined character.  My current gear gives me resistance to physical attacks and the dreaded light/dark attacks (which can instant kill when user smirks).  I cover the other elements with the rest of my team's resistances.

Siddhartha's moves, a mix of offensive and support magic.  Ice age and judgement light are single target and multiple target severe damage spells respectively.  Energy drain prevents me from running out of MP and heals my HP, but its offensive power is low and it takes several turns to refill my MP.  Concentrate makes my next magic attack do 2.5x damage, meaning it's better in terms of damage per turn and MP economy.  Doping raises the party's max HP during battle.  Luster Candy is an all party buff spell that raises Phys/Magic Attack, Defense, and Hit/Evasion, and stacks up to 3 times.  Salvation is full party heal that also cures ailments when smirking (one of the only smirk abilities I dislike, if I'm status'd I cant get smirk to cure myself!  Old salvation didn't require smirk, but its high MP cost balanced it out versus less comprehensive alternatives).  Awakened Power gives me pierce (ignores all resistances except reflect, but pierce is glitched in this game and goes through reflect too) and a sizable flat damage bonus; frankly it's OP and I don't understand why I get this ability when I'm not on Dagda's ending route.  The ability to directly command and switch between my human helpers in battle would fit much better.

For my app selections, I've got the must have demon fusion, map, demon weakness analysis, and skill slot boosters for myself and my demons.  I also have fusion level limit +15 (something I did very early in the game to get ahead of the power curve), 7 additional reserve party slots, 20% off buying demons from my compendium (lets you buy back demons you've previously contracted with), and a lot of apps for negotiation skills.  This latter group includes nearly all of the scout (recruitment) tree, truce for dealing with the very low odds of running above normal difficulty, fundraise (needed to clear a sidequest, otherwise a waste of points), a heavy investment in trade to get rare items, an experience boost for winning encounters diplomatically, and both Demon Charmer AND Threatening Aura to play good-cop/bad-cop.

Next up is Shiva, the god of destruction and rebirth, at maximum level.  Shiva hits single targets like a truck with physical attacks, and Akasha Arts can pierce if he's smirking.  He drains Phys, Fire, and Lightning, and is immune to mind status ailments with no weaknesses.  I also gave him Tetrakarn (grants party phys reflect for one turn) and Imposing Stance (User cannot make further moves this turn, reduces enemy press turns by 1) for support.  A very strong ally, whose only weakness is a lack of coverage and no smile charge for guaranteed pierce.

Krishna, Vishnu's avatar and the main antagonist of the game until recently.  His plan to stop God involved creating a new universe where all are one, whereas I introduced him to my plan of peace through superior firepower and a katana through the gut.  One backtrack to where I originally met him and a brief conversation later, and he came around to seeing things my way.  A magic build like me, Krishna actually has only a single attacking move and poor resistances.  However, he is still one of my strongest party members, carrying an all around buff, an all around debuff, doping, a spell that revives and summons an ally (meaning he can take over summoning duty if I fall), and the absurdly good ability to use healing and supporting items to essentially have any healing/support ability at his fingertips (normally only the protagonist can use items).  He also has a status ailment spell that inflicts every mind ailment while lowering enemy defense (he has one that inflicts poison/sick/bind too, but I had him forget it before coming in here).  His only downsides are his crap resistances, below average HP, and having no way to regen his MP beyond a few precious items.

Mastema, a very sketchy angel.  Repels four elements while only being weak to one.  He has the same offensive spells as Siddhartha, including energy drain, but also has passive abilities that greatly increase ice and light damage.  However, he lacks natural pierce and has Smile Charge in place of concentrate.  To round out his smirk happy nature, I gave him the support spell Magaon, which removes smirk from the enemy.

Another angel I've somehow shanghai'd into fighting God.  Seraph is basically Mastema, but with more (weaker) resistances, weak to a different element, and has Fire and Gun attacks in addition to Judgement Light and Energy Drain (but no Ice).  Carries Salvation in place of Magaon in the support/healing slot.

SMT's God is basically the demiurge, so I'm pretty perplexed by this guy being willing to help me.  Anyways, Demiurge is a mixed bag.  He has the crazy powerful Anticthon spell that is severe almighty damage plus debilitate to all foes, but anticthon now requires smirk for the additional effect and is super MP expensive.  Worse yet, Demiurge has shit MP and no way of recovering his MP.  He'll likely only be good for a single battle.  He'll be REALLY GOOD for that battle, but that'll be it.  He does also have the Lightning God's single target spell, which isn't as MP hungry.

Inanna, Mother of All, was part of Krishna's Divine Power's faction.  Her role, to continuously given birth to new gods (and rebirth ones demonized by God) to supply the Divine Powers with an army and make themselves invincible.  Until I defeated her and forced her to join me that is.  Inanna has superb elemental coverage with low cost severe fire/ice/force/lightning spells and concentrate to power them up (these unique spells do come with the cost of making her weak to the opposing element after use).  She also has debilitate and imposing stance for support, and a LOT of MP to make use of.  Beyond the downsides to her elemental spells, her only other glaring issue is her shitty, shitty HP.  Without doping applied she risks dying even when max buff/debuff stacks are applied against tough encounters.

Another member of the Divine Powers I've beaten and later recruited.  Odin is honestly not one of my stronger gods.  However, he has the useful ability to use items, a phys move that pierces without smirk, some decent lightning attacks (Thunder Reign would be great if it could pierce, but alas it cannot), and the outdated but still useful ability to lower enemy defense (and only defense).  He's also got a repel gun resistance, which is rare and might come in handy.  Since he's not boss fight material, he'll actually get used a lot to help clear mobs.

The Egyptian god of storms, deserts, and foreigners, Set is a character I really, really like in the series, but his appearance here will not be very glorious.  Set is on trash mob duty, pure and simple.  He has greatly increased force damage, but this is undercut by his best spell is only heavy damage and low magic stat.  His strength is decent and Rending Claws is a good move, but without pierce too many enemies resist physical at this point in the game.  He has Luster Candy and Makarakarn (reflect all non-almighty magic for one turn) and a passive ability that amps his hit/evade rate, but lacks the MP to keep up the support spells over a long fight.  What Set DOES have is a powerful auto-attack and the Makajamaon (seals/silences all enemies) spell + an affinity for ailments.  This lets him pound on random enemies for no MP and shut down any dangerous mobs/bad situations.

The Japanese creator goddess who died and became a death goddess.  Izanami is here for one reason; she is the only party member I have with decent magic who possesses a powerful Dark elemental attack.  My only other access to the element with this party is using Mudoon stones with the protagonist.  She carries Thunder Gods for additional elemental coverage, as well as concentrate AND smile charge to pump her damage and proc extra effects.  Also carries a full party healing spell and spell that grants immunity to a single light or dark spell to each member of the party.  Poor HP though.

Those present but not shown include:

• Mara, a physically inclined attacker with a unique multi-hitting physical move that does great damage and lowers defense when smirking.  Has charge AND smile charge, much like Izanami but for physical.  Also has an all hitting charm spell and Thunder Gods for coverage.  Not depicted because his/her design looks a LOT like a dick.
  
• Mitra-Buddha, the last of the major Divine Power's bosses I previously defeated.  Honestly, really disappointing.  Sky high attacking stats, but pitiful, pitiful MP and all of his moves are MP expensive.  Has two weakness, unheard of for this point in the game, likely to proc his (not yet learned) unique ability that boosts all his stats when hit by something he's weak to.  However, that's not even a good ability, since he'll still take a lot of damage and it can't go higher than the usual limit of 3 stacks of buff.  He might be able to power through one fight to earn his keep, much like Demiurge.
  
• Huang Di, the Yellow Emperor, has Demiurge/Mitra's issue of having jack all for MP while possessing some of the strongest, most MP expensive moves in the game.  Unlike the others, this isn't my fault; as a famed, he resulted from a fusion accident, meaning I had no control over his skills.  Unlike Demi and Mitra, Huang has a good mix of attack and support skills including four different attacking elements, Salvation, and Luster Candy.  Like the others in his situation, he'll be good for one boss battle.
  
• Throne, an angel 30 levels below the average party member that will act as an out of battle heal-bot to conserve other's MP and items.  Knows a revive spell, an ailment healing spell, and an all party healing spell.
  
• Vetala, a random crappy demon along for the ride.  Will probably get]no use unless I'm desperate.
  

[*]



Besides the gods and demons, since I turned down Dagda's "kill everyone" plan I also have human allies backing me up.  Unlike my supernatural zoo, I cannot control them directly, they act on their own for better and for worse.  Luckily, they're pretty smart for the most part.  I'll mostly be using Hallelujah (high offense magic user who can also grant an endure effect to the party or preemptively ward against ailments) and Isabeau (jack of all trades who can attack with any element, heal, and buff, but not as well as any of the others).

Emancipation: Reverted to Base BtS Values
Mercantilism: +1 free specialist, Medium Cost, requires Banking.
Free Market: +1 Trade route, +25% Trade route Yield, High Cost, requires Economics
Free Speech: +1 commerce from villages, +3 commerce from towns, +100% Culture, Low cost, requires Economics

Creative: +2 culture per city. +100% production of Theatre. +35% production of Library, Observatory.
Charismatic: Charismatic: +2 happiness. +1 happiness from Broadcast Tower. -25% XP needed for promotions. +100% production of Colosseum, +35% production of Library.
Imperialistic: +50% production of Settlers. +100% Great General points. +100% production of Custom Houses.

Colosseum: +1 happy, +1 happy per 20% culture slider, +1XP to melee, archery, mounted and seige units. Cost 80 hammers, requires Construction
Babylonian Garden: +2 health, +1 happy per 20% culture slider, +1XP to melee, archery, mounted and seige units. Cost 80 hammers, requires Construction
Mayan Ball Court:  +3 happy per 20% culture slider, +1XP to melee, archery, mounted and seige units. Cost 80 hammers, requires Construction
Greek Odeon: +3 culture, +2 artist slots, +2 happy, +1 happy per 20% culture slider, +1XP to melee, archery, mounted and seige units. Cost 80 hammers, requires Construction

Taj Mahal: Triggers Golden Age, +2 Great Artist points/turn. Cost 700 hammers. Requires Nationalism (No production bonus from marble)
Mausoleum of Maussollos: +50% Golden Age length. Cost 450 hammers. Requires Calendar. Obsoletes at Nationalism (No production bonus from marble)

Crossbow (and unique units): +25% defence against macemen
Maceman: Melee unit, strength 8, +50% against melee, +25% against cities, cost 70 hammers, requires Civil Service, Machinery, [copper or iron].
Samurai: Japanese Unique Unit: strength 8, starts with Drill 1, 2 free strikes, +50% against melee, +25% against cities, cost 70 hammers, requires Civil Service, Machinery, iron. J
Impi: Zulu unique unit: spearman replacement: Strength 4, 2 movement points. +100% against mounted units, -40% against archers. Cost 35 hammers, requires Hunting, copper or iron.
War Chariot: Egyptian Unique Unit: chariot replacement: Strength 5. +100% attack against axemen, -25% attack against archers. Cost 30 hammers, require horse, Wheel.

Changes from base BtS, found in CIV4EraInfos.xml)

Classical: 2 settlers, 100% tech cost
Medi: 80% tech cost
Ren: 40% tech cost
Industrial: 35% tech cost
Modern: 30% tech cost
Future: No changes