AI has an ascension crystal. What are my possible courses of action?

1. You could grab other ascension crystals. If you were to grab at least 3, you could ascend in 334 turns. However, the AIs will not like that you are ascending, so you would likely find yourself attacked by multiple AIs.

2. You could pay another AI (or several) to declare war in the said AI. That attacking AI(s) might get around to destroying the ascension starbases.

3. You can sit back and wait for the other AIs to take care of it on their own. They don't like other civs trying to ascend, so they will try to declare war on their own.

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Overall, ascension victory is one of those victories that is going to involve a lot of warfare. No one likes someone else trying to ascend, so they will try to stop it by force. The only way to avoid wars is to be strong enough that no one will dare attack you while you ascend. Arguably, if you are strong enough to win by ascension victory, you are probably strong enough to win by conquest victory.

If the countdown is at 400, then the AI has most likely two crystals. The Ascension victory requires 1000 points, and each crystal provides one point per turn.

As for possible actions, well, there aren't many. You could try to find and capture the other three crystals. If you are quick enough, you may beat the AI to the Ascension victory (but it will be close). However, the other races won't take kindly to your attempt to ascend, and will most likely declare war soon.
You could also try to go for the Tech victory. 400 turns should be enough to do that. Just make sure, that the AI doesn't capture another crystal.
Lastly, there is always war. However, you don't have to fight yourself. You can try to bribe another race to go to war against the one trying to ascend. Before you do that, though, place a combat ship next to the ascension starbase, and then give it to the race you want to bribe. With any luck, they will destroy the starbase for you.

Well, I hope this helps.

Edit: ...and ninja'd.

I doubt that money could fix this issue, so research all the influence, invasion and weapons techs you can and go full-on war.

it is the only option.(try to get everyone ganged up on them too.(and do not forget defences)).

hi, let me ask, when playing on meta verse, do i play with agaisnt AIs???? or other internet players??

There is no multiplayer for this game. Not a whole lot of people were interested back when polls for it were up. So it is just AIs. You use metaverse to play a game, get a score, and post it online.

From what I understand, the game handles everything such as posting the score online and making sure you aren't cheating.

If that AI is at war with another AI (or you can bribe an AI into starting such a war), it may be an interesting experiment to donate an armed ship next to the ascension starbase to the warring AI. With some luck it attacks the starbase, leaving your good name unscathed.

Let him ascend.  It takes 400 freaking turns.  Declare war and take out his ascension crystals 300 turns from now, assuming another AI hasn't done it for you.  

I always turn off Ascension victory because I find having that time limit annoying.

even if they take all five crystals, it would still take almost 200 turn for them to gain victory. at that point, you would have a fleet of armadas or maybe a planet full of golds. i have done this ascension victory thing, and the only way to do it is through absolute military dominance. if you bring the said AI's military down by giving more military ships to the opposing AI or go on the war path against the controlling AI yourself just to bring his military down, then he will be very unlikely to achieve the ascension victory. not to mention the said AI will not likely gain much of support from the other AI when they control the ascension starbase. they also get attacked more often which shifts other AI's attention from you. unless, you tick the other AI off as much as they do against the Ascension base controlling AI. some AIs are extremely passive, you really need to provoke them to do something before they become aggressive against those kind of thing.

The AI can make a very serious run at an ascension victory, but in 30+ games of Twilight I've seen it maybe twice. You don't need to worry unless the countdown reaches the hundred-turn mark.

Or less.

Anyway, the best course of action is to:

Step 1: Attempt to buy the bases.

Step 2: Declare war

Step 3: make everyone else declare war, even the minors.

Step 4: research the defense for the weapon branch the AI uses, and research another weapon type, (AI: MDs, You: Beams.)

Step 5: Conquer

Step 6: Repeat with every AI as they try.

As some have said before: you really aren't in any trouble if the AI ascends in 400 turns and you don't want to go to war.

400 turns is an awful long time (over 8 game years), during which a LOT will happen, including most likely wars started by other AIs to kill the ascension starbases. Ascension is really a worthless victory path. Anyone strong enough to defend an ascension victory, could (even if holding all 5 crystals, reducing the time to 200 turns) more easily wipe out all intelligent life in the galaxy instead, while others will be much quicker to a tech victory. I don't consider ascension SBs a problem unless I have 50 turns or less to act (which never happens, really), by then I'd generally be at war with the culprit anyhow because he's too strong to resist picking on me (and will die for the insolence).

I like twilight of the Arnor but I thought this was stupid I never play with it on.