I entered a battle with a Nightfall Captain and defeated it, but the battle didn't end. The turn the Nightfall Captain died, I got a popup saying my first pet did not have a target selected. The full battle log is below:

You have begun a battle!
Turn 1: Eos's Malgorus' Familiar (Rank 21) hits Nightfall Captain for 6,243 Magical Damage!
Turn 1: Eos's Conflagrate Critically Hits Nightfall Captain for 24,304 Pure Damage!
Turn 1: Nightfall Captain has been afflicted with Inferno!
Turn 1: Un-named has gained Thorncoat!
Turn 1: Selene's Fairy Light hits Nightfall Captain for 4,960 Magical Damage!
Turn 1: Selene's Fairy Light Heals Un-named for 0 Health!
Turn 1: Selene's Fairy Light Heals Selene for 0 Health!
Turn 1: Selene's Fairy Light Heals Eos for 0 Health!
Turn 1: Nightfall Captain's Piercing Wound hits Un-named for 107 Physical Damage!
Turn 1: Un-named's Thorncoat hits Nightfall Captain for 2,604 Physical Damage!
Turn 1: Selene's Vaeluna's Grace Heals Un-named for 107 Health!
Turn 2: Eos's Malgorus' Familiar (Rank 21) hits Nightfall Captain for 5,445 Magical Damage!
Turn 2: Eos's Malgorus' Familiar has increased to Rank 22!
Turn 2: Eos's Inferno hits Nightfall Captain for 23,869 Pure Damage!
Turn 2: Eos's Fireball hits Nightfall Captain for 4,649 Magical Damage!
Turn 2: Un-named's Leeching Strike hits Nightfall Captain for 1,086 Physical Damage!
Turn 2: Selene's Beam hits Nightfall Captain for 2,234 Magical Damage!
Turn 2: Selene's Beam Heals Un-named for 0 Health!
Turn 2: Selene's Beam Heals Selene for 0 Health!
Turn 2: Selene's Beam Heals Eos for 0 Health!
Turn 2: Nightfall Captain's Piercing Wound hits Un-named for 119 Physical Damage!
Turn 2: Un-named's Thorncoat hits Nightfall Captain for 2,412 Physical Damage!
Turn 2: Selene's Vaeluna's Grace Heals Un-named for 119 Health!
Turn 3: Eos's Malgorus' Familiar (Rank 22) hits Nightfall Captain for 5,773 Magical Damage!
Turn 3: Eos's Inferno hits Nightfall Captain for 20,464 Pure Damage!
Turn 3: Un-named's Leeching Strike hits Nightfall Captain for 1,157 Physical Damage!
Turn 3: Eos's Flamethrow hits Nightfall Captain for 8,017 Magical Damage!
Turn 3: Nightfall Captain has been afflicted with Burning!
Turn 3: Eos has gained Engulfed!
Turn 3: Selene's Beam Critically Hits Nightfall Captain for 4,603 Magical Damage!
Turn 3: Selene's Beam Heals Un-named for 0 Health!
Turn 3: Selene's Beam Heals Selene for 0 Health!
Turn 3: Selene's Beam Heals Eos for 0 Health!
Turn 3: Nightfall Captain's Piercing Wound hits Un-named for 131 Physical Damage!
Turn 3: Un-named's Thorncoat hits Nightfall Captain for 2,180 Physical Damage!
Turn 3: Selene's Vaeluna's Grace Heals Un-named for 131 Health!

I think it could be related to the fact that the enemy was killed by thorncoat damage, but battles with other enemies (including with another Nightfall Captain) ended normally when they died from thorncoat damage.


By skipping turn on all pets I was able to get to the victory screen:
Turn 4: Un-named uses Block to take up a Defensive Position!
Turn 4: Selene takes no action!
Turn 4: Eos takes no action!
Your Party was victorious! You defeated 1 Enemy!

It could also be caused by the damage adding up to exactly 120,000

Not really sure what would cause this. Also seems to be an exceptionally rare occurrence. I haven't heard of this happening in a long time.

Checking through the code real quick, Thorncoat does a proper 'check if unconscious' check and it's clearly looking for health values <= 0, not just < 0.

Without more information or a sure fire way to replicate this, I don't think I'm going to have much luck figuring it out.

Fortunately, it's a pretty minor issue as, as you mentioned, you can just skip a turn and then the battle will properly end.

If you or anyone else has this happen or can provide more information, let me know.