Temporary party members (rm xp)

I wwant to know how to make a party member like a hireable mercenary that when he is dead he is removed from the party FOREVER

make a common event.

Conditional branch: If CHARACTER HP<=0, remove from party.

else: nothing

If there's nothing in the else part you can just get rid of it entirely by unchecking the "Set handling when conditions do not apply" part at the bottom of the conditional branch box, but that's trivial.

Also, it may be better to check for a knockout state, since there is a chance that having 0 HP would not mean being knocked out during the battle, and whatnot.