What are your strategies for taking the Guardian as early as possible?

[Arnuz]

Are you really sure it is doable with NPGs? I'm not sure it could be done, at least not on Impossible or even at Hard. Maybe only on Average or lower difficulty levels.

You're probably right
If available I'd use mass drivers anyway.

[RefSteel]

Are you really sure it is doable with NPGs?

Yup! You just need a lot of them! Shield-halving weapons round the resulting shield level down, so the Impossible Guardian's Class IX shields get cut to de-facto 4, and NPGs do 2-5 damage per hit. Now, this does mean your NPGs are averaging just one damage (against its 10,000 hitpoints!) for every four hits, but with enough of them, you can indeed break through.

In general, I think attacking Orion may well be worthwhile in a huge galaxy, but I haven't played one of those since ... probably that Silicoid Imperium that Cyneheard mentioned!

(Note in MoO2, I'm pretty sure Orion was just another really nice system with a really powerful "space monster." The special victory path came from attacking Antares, which you could reach via a special tech leading to a special building project which you could complete anywhere in your empire. It's possible that taking Orion was guaranteed to give you the tech, among others, if you didn't have it yet; I'm not sure. It's been a long time since I played MoO2....)

[SpaceOWL]

Are you really sure it is doable with NPGs?

[...]Now, this does mean your NPGs are averaging just one damage (against its 10,000 hitpoints!) for every four hits, but with enough of them, you can indeed break through.

1 damage in 4 hits is still super optimistic... the Impossible Guardian has beam def = 9... so if you less thah BC5 you will hit no more than the minimum 5% - and only a critical hit (1 or 2 chances in 100) will cause that 1 damage.
Even harder if the Impossible Guardian really has Adv. Damage Control (IIRC it doesn't due to a coding bug)

[Bionic Commando]

(Note in MoO2, I'm pretty sure Orion was just another really nice system with a really powerful "space monster."  The special victory path came from attacking Antares, which you could reach via a special tech leading to a special building project which you could complete anywhere in your empire.  It's possible that taking Orion was guaranteed to give you the tech, among others, if you didn't have it yet; I'm not sure.  It's been a long time since I played MoO2....)

Ref -- you're correct. Orion is not a victory condition in MoO2, although it gives you extra bonus points for your High Scores board along with the usual sweet planet and tech bonus.

Even at the highest difficulty levels, it was possible to take Orion with fairly limited tech -- there was a way to beat it with heavily modified Merculite missiles for example. You could also use Gyro destabilizers. In either case, the Guardian was beatable within 100 turns. Loknar and the Avenger were good enough to ward off tons of AI fleets as well, so beyond the techs and sweet planet you got something that was potentially game-turning. It could also accelerate your timeline for attacking Antares which was also a victory condition. My feeling is that Orion could substantially shorten MoO2 games.

The issue with MoO1 is that Orion isn't a differentiator nor a victory condition. Perhaps that's the answer -- create a variant where beating Orion is winning the galaxy. Could make games shorter than getting to the 2/3's council majority. I'll also cop to not playing much on large or impossible, so it's possible Orion is super useful for beating runaway AIs.

[RefSteel]

1 damage in 4 hits is still super optimistic... the Impossible Guardian has beam def = 9... so if you less thah BC5 you will hit no more than the minimum 5% - and only a critical hit (1 or 2 chances in 100) will cause that 1 damage.
Even harder if the Impossible Guardian really has Adv. Damage Control (IIRC it doesn't due to a coding bug)

Oh, I wouldn't suggest taking on the Guardian without advanced battle computers - but Mrrshans can actually hit it with 20% of their shots with starting CPUs! The question was whether you can kill it with NPGs, and the answer is definitely yes, but even as cats with BC11 and battle scanners, it certainly isn't efficient!

[SpaceOWL]

Just to add an example, I played a nice game yesterday where I had no choice but to take out the Guardian to win. 3 of the 5 AIs have some crazy combination of shields (Class VII to XIII deflectors + Planetary XV or XX), and no one had any bombs better than Fusion... 

So after one more inconclusive galactic council, in 2500, I decided to go get the Death Ray to shake things up.

I was playing Medium galaxy at Impossible level with the Mrrshan (yes yes you can call me a masochist ). 

This is the fleet I used:
   
   

After avoiding the 5 rounds of scatter-X (just a single hit and you're toast) and losing some ships to the other weapons, I started hitting back with some 800-900 ships left, for 1000-1600 damage per round.

These are the brave heroes that survived the fierce battle:
     

Got Death Ray, Scatter Pack X, High Energy Focus and Hyper Drives. Not bad, but needed even some more tech levels to fit one DR +HEF in a large hull and build a doom fleet with 70-80 ships to start glassing everything at sight...

Long story short: 
I don't see much of a way to get to Orion any sooner or with much less than that kind of fleet. Of course Mrrshans have a +4 benefit so you can do it with a smaller stack and not so high BC level.
But if it wasn't for the crazy shield levels AND the lack of any bombs, I wouldn't even need to get Orion to wipe out the opposition. I already had the money and good techs to win the game. I just needed the can opener. 

[Cyneheard]

I was playing Medium galaxy at Impossible level with the Mrrshan (yes yes you can call me a masochist ). 

Nice job! There's a reason Mrrshans are last on my list. 

[rgp151]

I don't often take out Orion, but I've definitely had games where it was important, especially on Impossible. It can be a way to come back from behind. But worse is when the AIs get it, which they sometimes do.

Around Megabolt Cannons is when I'll consider going after it as well. Often with Megabolt Cannons, Phasos, Auto Blasters and Gauss-Auto Cannons with no HEF are what I typically use as the main attacker. Put those on Medium ships with high battle computers, high maneuverability or subspace teleporters if its that late. If I don't have subspace teleporters I'll typically make 2 or 3 different similar attackers so they can all close in on him. With teleporters I'll just make one super stack.

But there is little need to go after Orion when ahead, other than just to ensure that the opponents don't get it. In close games or when I'm behind, that's when I'll go for it.

[Psillycyber]

The Mrrshans are well set up to take on Orion early-ish in a cost-effective manner. They basically need to be able to fit megabolt cannons and combat speed 4 on a small ship. The combat speed is needed to dodge the Guardian's missiles. Combat speed 4 means either ion drives or fusion drives + inertial stabilizer. But even if you rely on fusion drives + inertial stabilizer, you are going to need high tech levels in the 30s in propulsion anyways in order to fit everything on a small ship, so it actually makes more sense to aim for megabolt cannons + ion drives.

To fit ion drives with the best manuerability and a megabolt cannon on a small, one needs roughly level 25 in construction, level 36 in propulsion, and level 30 in weapons. Those numbers can be fiddled with, where a lower level in one of the areas can be compensated for by a higher level in another area, but that is the gist of it. (Plus, if you are using megabolt cannons and ion drives, your tech levels are bound to be about that high in those categories anyways, even without a bunch of extra techs acquired at each rung).

You'd need about 3000 of these smalls to be safe. I reckon the earliest one could consistently pull it off would be 2450.

[SpaceOWL]

It's doable with much less ships (I pulled it off with about 1000 ships) and with combat speed 3 (altough it requires the player to have some skill in combat screen). See my post above.

Maybe with 1/3 of the ships it could be pulled off even earlier than 2450.... That could be a good background for an Imperium game (if it hasn't yet been done)