Details about fallen-spire endgame mechanics

[ColdPrototype]

I've beaten the fallen spire campaign a few times on my own, but I recently was playing it for the first time with a friend. Things were going well all game, with us repelling the waves from even the transceiver shard without losing too much. However, the first few waves spawned by the transceiver were virtually unstoppable. We had taken down a few Mk I Hunter-Killers as part of the last chase/exo-galactic attack, but we were getting half a dozen Mk IIs in the first few minutes (with plenty more following them). Suffice it to say, it was sad too see what they did to spire dreadnoughts. So I've been wondering about the details of the attack, to see if there's any way I might be able to mitigate it. Are the final attacks dependent on AI progress? Because I could probably get that lower using the super terminal if that would make things easier. Or do I simply have to be absolutely rigorous with my long-term kiting of these beasts?

[keith.lamothe]

The maximum size of the fs exowaves is proportional to the number of spire cities you have, and has no relation to AIP at all.  Actually, a fairly recent change made the exowave-budget-increasing spread across the city hub and the city modules (shipyard, hab, reactor) so I guess in theory you could scrap all of those sub-modules at some point to reduce the max size of the exowaves, but I don't know if that would really help you (nor would I be content as a game designer to leave that as a valid tactic, just feels wrong for several reasons).

Anyway, the addition of HKs to the list of ships that can be picked for exos is also a fairly recent change.  I've heard some feedback about the pain they can inflict, but I don't recall anyone saying they presented a total brick-wall to progress (at least not at this stage of the game).  So it's possible they're a bit much but I think you can probably eke by during that last 30 minutes or so:

1) Know where the HKs are.  And anything else that is truly a threat.
2) Have your spire capital fleet waiting for each HK as it emerges from a wormhole (any wormhole will do, so long as you aren't under particularly withering fire), so that you're right on top of the HK and it doesn't get to use its range advantage, and just blast the thing to smithereens.  Nothing in the game can withstand the full firepower of a spire fleet for very long, though you are still going to suffer losses.
3) As an alternative to 2, only face the HK while your fleet is under spire city shields (and not human ffs, as the human ones reduce outgoing firepower).  Normally I place my cities covering inward-facing wormholes but in theory you could put one right next to one that you know the AI has to come out of to get to your homeworld, and tear it up good right as it comes out (but they can then still rush past you to the next wormhole, if they survive).
4) Defense in depth. 
- The normal speedbumps (an ff over every inward-facing wormhole) won't actually slow down an HK much if at all, but a significant defensive bulwark (a spire city, or a big pile of human ffs) can. 
- Also, sheer distance can work in your favor: the exos have to spawn from an AI planet, so before starting the transceiver-attacks phase you can take your spire fleet and do a clear-cut of all AI planets out to some distance.  AIP will go through the roof, but that won't be an issue unless you have golems-hard or spirecraft-hard enabled (and even then it probably won't make the difference between win and lose in this particular case).
5) If you do have spirecraft, I commend implosion artillery to you for HKs and anything else with an unsanitarily-high max hp.  Rams may also be good, haven't tried those much myself.

Good hunting

[bongotron2000]

5) If you do have spirecraft, I commend implosion artillery to you for HKs and anything else with an unsanitarily-high max hp.  Rams may also be good, haven't tried those much myself.

I've tried Spirecraft Rams, but never had any luck with them. They always got one-shotted by the HK before being able to collide. Maybe they'd be more likely to get through while waiting on top of a wormhole for the HK.

As you said, the Spire fleet is the best for taking out the HK, though admittedly, I've never faced six MkII HKs.    I tend to keep a few transports near the fleet so they can respond quickly if needed.

[atomjack]

Rams are useless against HKs: they have a multiplier of 0.001 against command-grade armour.

I second the advice on camping an incoming wormhole - even HKs go down fairly fast when faced with 40-50 frigates. If otherwise overwhelmed, though, I have managed to whittle them down with a smaller fleet with lots of manual kiting. Just keep your fleet out of range and chip away at it over 4-5 planets.