There are two issues here (disjoint? possibly related).  Items are numbered chronologically (so they're not separate issues; it's all one big report :)

Win 10 (64-bit), 1920x1200

Version V1.5.13 S3 (64-bit)

0.  Totally fresh launch of Endless Legend (so no previous game lurking in memory), loaded Turn 128: Vaulters, Normal/Normal, large vs. 8.  [All save files attached below]

0.  On Turn 128, I control 6 of 8 original capitals, yet I have not already won the game via Supremacy.

[_] When a player loses its capital but has other regions surviving, does one of them get designated as a new capital?  That would explain it.

~~~~ (defeated) ~~~~
2.Lireisy - Liloriel/Broken Lords
3.Djoul - Cadne/Cultists
~~~~ (still in play) ~~~~
4.Utharan - Shkent/Roving Clans (truce)
5.Yerurnqua - Natoli/Ardent Mages (war)
6.Lorw - Piche/Wind Walkers (war)

On Turn 128, I am sieging the last 2 capitals:
7.Ostakk - Kuru/Forgotten (war)
8.Wervalyn - Theramanya/Drakken (war)

1.  At start of turn 129 [autosave], both besieged AIs attack my siegers.  I win at Wervalyn, draw at Ostakk (because 6 rounds was not enough for it to bring in 14 reinforcements).  Thereafter, both capitals are empty, with 0 garrison, 0 militia.

2. On turn 129, I promptly attack both capitals, win both fights (Wervalyn by walkover because it's empty), yet neither of my groups walks in, and neither region is conquered.  Thereafter, attempting to walk in pops up the usual Attack-or-Siege battle selection window.  I expected that winning a city-attack conquers a region; that's how I conquered the previous 5.

[_] Do both Forgotten and Drakken have a special ability that can prevent an enemy group from walking in after winning a city-attack?

3. During turn 129, I trigger the quest Colossal Danger, which creates a Skoros in Ostakk, about 40 hexes away from my capital of Yiggodra.  I decide to ignore him.  (Note: If you replay from the T129 autosave, you might not get this event.)

4. On turn 130 [autosave], I attack Skoros with the Ostakk group (hero + 6), with my Wervalyn group (hero + 6) as reinforcement.  I set up everybody out-of-range of Skoros, except two flyers.  On Phase 1/6:

4.a) Skoros shoots an Ended at range 2, and gains Mind Control.
4.b) My units move closer.  A Marine shoots Skoros once (for -111)
4.c) The Ended (under Mind Control) now swings at an adjacent Dredge.  No other group is adjacent to these two.  During the Ended's swing, there are three damage pop-ups: a "0" (which must have been on the Dredge), a "-146 standard hit"(?) (can't tell on whom), and a "+146 healing" on Skoros(?!).  There was no effect in play that would have granted healing.  No unit in the Initiative bar between the Drudge and the Ended has any healing ability.   The Ended has Chain Lightning, but nobody else is adjacent to the Dredge, so it should not have triggered.

4.d) EL hangs in the middle of Phase 1 [screencap][savefile].  The battle simply does not proceed to the rest of the Initiative list (an Arpuja and two Caecatori).  In the Init bar, the Dredge and Ended's tiles are still highlighted.  The battle timer button still shows "Phase 1/6", and never proceeds to "Finish".  The "End Turn" button says "Turn 130 Battle Mode", and is grayed out.  Clicking on any unit does not cause their stats card to appear.  The rest of the game UI is not affected, and I can zoom out, pan around, and access all of the global info windows, all cities and spy reports, and look at all groups in sight, including the 3 groups involved in this battle (except that looking at Skoros's world map card does not show his current damage).

4.e) Damage is shown in the units' Initiative tiles.

- 914/1024 Skoros: This must be the -110 from the one hit he took.  He did not get healed.
- 090/160 Ended: Consistent with -70 damage from Skoros's one shot.  He didn't get healed.
- 291/291 Dredge: Inexplicable.  He must have gotten healed!  This miiiight be explained as: Ended hit Dredge for -146, bug instantly healed Dredge for +146.

Conjecture #1: When Ended under Mind Control attacks frenemy in melee, its Chain Lightning triggers as Healing instead, and hangs.

Conjecture #2: "It's Skoros's fault." -- Gios

Attached files

T128 savefile

Yiggodra - T128.zip

T129 autosave -- The two AIs will attack your besiegers.  Win both, then attack both of their capitals.

Yiggodra Skoros - T129.zip

T130 autosave -- Dogpile onto Skoros.  Set up the Ended in forest near him (as bait), everybody else out of range: hero + Marines + Caecator back left, Dredge + Arpuja back right.  The only target in range for Skoros in Phase 1 is the Ended.  Arpuja will fly up left touchline :), blocking that path, forcing Dredge to veer to the center and end up adjacent to the Ended.

Yiggodra Skoros - T130 - autosave.zip

T130 mid-battle (it's already hung now) -- and associated text files

Yiggodra Skoros - T130 - battle hung.zip

diagnostics output registry.zip

Reproducibility:

Unknown -- possibly stochastic.  I reloaded the T130 autosave, replayed the combat, set up differently, and Skoros shot the Arpuja instead, and didn't get Mind Control.  Skoros is worth only 2.8 x 14 = 39 XP?  Really?  meh -- I get more than that when a Settler retreats