(v23, linux, HB)
See hp of Elena:
HowTo reach negative HP: Just continue (deliberately) loosing a battle after battle without healing in between... When you're harmed, in-battle maxHP is lowered each time and unless healed at home, you will start the next combat with this number. After a point, think I launched with 2/2HP and on the next hit it made maxHP negative. The character is incapacitated as expected, except when returns home his HP is negative. Then the real fun begins...
Wanted to launch a lieutenant battle afterwards and it fully crashed the game. After this loaded the autosave with negatives and can launch the battle all right.
Some observations from battling with negative allies:
-- The battle starts with negative allies visually standing. I can do re-position.
-- It skips turns of negative allies (except for the first Sam's).
-- Enemies go after those with positive hp. Nobody likes to hang out with negative people after all.
-- Once all positive allies are down, the next round the game declares defeat and debriefing says 4 incapacitated.
-- Similarly, if I start the battle with all negatives, it let's the game play the whole first round and on the next one declares defeat.
Untested any other implications. All in all the issue can be easily repaired by resting.
Perhaps nobody ever will do such thing as this. Not sure I would count on it though. Perhaps something like adding a simple condition safeguarding we always come home with >=1HP would work?