[Trexmaster]

I can explain that one, Dev.

The Youkai gained EXP because of what I assume to be a bug with monster mercenaries on death.

When killed, monster mercenaries grant EXP at the end of the fight as if they were an enemy mob, like the Firespitter shown in the picture self-detonating to kill itself and end the fight, hence the EXP earned for the debug battle.