Spell Very Rare Treasure

[Sapher]

it's highly assymmetric, and unlike wizards' pact, this doesn't give any benefit for the player in exchange

You can give something to a player in return. It can be protecting players lairs, or removing penalty of moving into AI's territory during a wizards pact. Or something else...

[Seravy]

I can't make the AI not take your lairs, I'm not capable of that. I also shouldn't because lairs are often obstacles that block access to parts of continents.
Changing game rules elsewhere isn't giving something in return. The player doesn't get a choice of "yes, I do want a Lair Protection Treaty so I don't attack your lairs and you allow me to enter your territory and backstab you despite a wizard's pact in exchange." or not wanting to have that treaty. It's not a package deal the player can get or avoid, one that's actually connected. The player will simply get angry about the AI taking their lairs and not allowing them to do the same, and would ignore the "benefit" because it's a separate thing altogether. They didn't receive it for that specifically, it's just there.

[Seravy]

Implemented as :

-Very Rare spell treasure will now be replaced by a random book/retort if time is before 1416 on Advanced and below, 1415 on Expert, 1414 on Master and 1413 on Lunatic difficulty.
-Rare spell treasure will now be replaced by an uncommon spell, and a 1600 value artifact, or that much gold if no more item slots are available if time is before 1410 on Advanced and below, 1409 on Expert, 1408 on Master and 1407 on Lunatic difficulty.

Feel free to suggest different dates if you think it's too early or late for the spells.
I still haven't seen any responses to whether we want rares to be included in this or not. Nor to whether the AI is too slow at clearing lairs or not.

This is a temporal implementation - the next version has to be released eventually so something had to be done to progress. But it can still be changed in future versions, so do post your opinion, even after the release. In fact, especially after the release, these sort of things are easier to "feel" than prove. If you got a spell too early and won in a way you feel undeserved, or the AI got one and overwhelmed you or ruined your game, let me know. If you consistently get all the lairs and the AI fails to have any, or the opposite, also let me know.  Provide details, like difficulty, date in historian, etc.

[massone]

Implemented as :

-Very Rare spell treasure will now be replaced by a random book/retort if time is before 1416 on Advanced and below, 1415 on Expert, 1414 on Master and 1413 on Lunatic difficulty.
-Rare spell treasure will now be replaced by an uncommon spell, and a 1600 value artifact, or that much gold if no more item slots are available if time is before 1410 on Advanced and below, 1409 on Expert, 1408 on Master and 1407 on Lunatic difficulty.

Feel free to suggest different dates if you think it's too early or late for the spells.
I still haven't seen any responses to whether we want rares to be included in this or not. Nor to whether the AI is too slow at clearing lairs or not.

This is a temporal implementation - the next version has to be released eventually so something had to be done to progress. But it can still be changed in future versions, so do post your opinion, even after the release. In fact, especially after the release, these sort of things are easier to "feel" than prove. If you got a spell too early and won in a way you feel undeserved, or the AI got one and overwhelmed you or ruined your game, let me know. If you consistently get all the lairs and the AI fails to have any, or the opposite, also let me know.  Provide details, like difficulty, date in historian, etc.

Played several games on 5.75 Expert recently with dual realm 4-5 spellbook strategies and I think the current turn counts for Very Rares don't make much sense. For Rares at turn 108, it's okay considering I finish most of my Rare research by then, so I can still get some spells not in my starting spellbook, but they come way too late compared to when I first start researching them (before 1406), so there's no chance of getting it "early"--which is acceptable, given the purpose of the restriction. But for Very Rares at turn 180, it means there will never be any Very Rares in Treasure, since the Towers don't give out VRs anymore, and those are the only encounters left by then (only because of the turn restriction on attacking those). The AI and I can clear the rest by 1411-1412. The only time they don't get cleared that fast is if we're wasting time warring with each other instead, in which case there might be 2-3 left by 1414. For an economy based strategy, I would have finished researching all VRs by then even with 30 or fewer cities on Huge, which is like somewhere between 33% - 50% of Arcanus' total territory. My first own VRs in normal research are finished research and cast by around 1410-1412, so locking VRs in treasure until 180 seems pretty excessive. Now earlier in the thread you mentioned you had a Great Unsummoning cast on you in 1412 by a Myrran Wizard in Expert difficulty because of Treasure and that was a problem, but in this version by turn 160 in 1413 it seems like every Wizard had at least 1 Very Rare researched. Myrran Wizard had both Fairy Ring active and cast Plane Shift only a few turns after 160, while I got Consecration just before turn 180 from banishing an Arcanus Barbarian Warlord/Guardian Wizard who had less than 10 cities for the entire game.

I suggest dropping the Rare limits by 12 turns across the board, and the Very Rare limits by 24 turns, to match the pace of research, getting them in treasure at around the same time that research/economy strategies can start casting their first spells of that tier, so that there's an actual strategic decision to be made between pursing military/heroes to access the advanced spells through treasure/banishment, or research. As it stands, there is no trade-off to be made--it's strictly optimal to be researching everything yourself, and use the encounters only to unlock non-starting spells if the encounters aren't already all cleared yet.

Better yet, make it three OR conditions instead of year. Having at least 1 spell of the relevant tier already available in the research list, spellcasting skill, or Fame. Each attribute makes sense from a flavor perspective--only a sufficiently powerful/learned Wizard can understand the treasure they found, and making it based on three different attributes means that you don't become forced to use Sage Master or other research plays to go treasure hunting. A Wizard who focuses on non-magical military strategies should suffer because the game is about mastering magic, unless their military exploits are so great they are famous enough to attract and buy help, which also adds value to this underused mechanic.

[Seravy]

Interesting. There have been players in the past who reported researching their very rares as early as you but I almost never get any done before 1415. I guess that depends on the player's skill level and of course various map or other settings.

According to the economy calculations where the research costs were decided, by 1418 (turn 216), players will have an average of 2 very rare spells researched. So that puts the time for starting the first one at around 1416. This does assume picking a "normal" amount of spellbooks of course, if you pick a very low amount you will finish faster and reach very rares earlier due to not having the spells to research. The AI might also finish faster on higher levels of difficulty.

What difficulty were you playing at? Very rares on all the AIs in 1413 sounds like Master difficulty to me (unless you had the bad luck of everyone being a theurgist sage master with low book counts). All the lairs being gone by 1411-12 also sounds like a very high difficulty level game. I normally have things left even in 1415+ on Advanced and Expert (unless I cleared them all myself which I rarely have the luxury of doing).

Enabling finding the spells based on own spell research is a good idea but I would prefer if the condition was "at least 1 very rare spell already researched". The jump between having one visible, and having one researched is very large.
The problem with this kind of restriction is that it takes away the chance of finding the spells from the less skilled players with research slower than average, and they are who need it the most.
I'm not sure what to think about casting skill and fame. They aren't hard to increase if you control enough cities, you only need to build the appropriate building for it. So this would add extra burden on human player while the AIs build everything anyway and would get the spells to early as a consequence.

Playing on different  land sizes messes with the research system because more land = more income = things get researched faster. I have no good solution to that problem at the moment. Mana and SKill scale with land size : you need to spend more mana and need higher overland skill to cast more overland spells if you want to conquer and hold larger territory. But this does not apply to spell research.
This is a problem in both directions - a game on Tiny land will be almost always over before anyone getting any very rare.
Maybe this is not even a problem, but a feature, I'm not sure. If we decide it is a feature and larger land should lead to faster advancement in spell tiers, then scaling the turn limits for spells by land size setting is something to consider.

You were playing 2 levels of land size above the default, and as a consequence feel spells should have been researched 2 years earlier. That would be fairly easy to implement, but only if everyone agrees this is the correct direction to take.