In OB64, which isn't too hard, when your characters die, you can only revive them in two ways: an Altar of Resurrection item (somewhat rare, and they are buyable but at a pretty high price) or at a Witch's Lair (which leaves them at low HP, costs based on the character's level, and requires you bring them to that town). If you don't revive someone before you defeat the enemy leader, that person will usually (not always, as cutscenes can interrupt it) become a Zombie, who you can then put into your army. Zombies get revived if they're killed unless the final blow was from a holy attack, but their attacks are pitifully weak and they get at most 2 of them no matter which row they're in, and if they're hit with fire they become skeletons, which are slightly stronger but still weaker than any classed human. If skeletons are hit by... I think it was a fire/air combo spell... they become ghosts, which don't attack, but put enemies to sleep (which kinda sucks, as you can get the same effect more effectively other ways). In short... in OB64 you don't want your characters to die either.

With certain items, female characters can become Angel Knights instead of Zombies. Angel Knights are pretty awesome - they don't attack very well and their stat gains are pretty horrid, but they evolve into Seraphs with the right stats & alignment. Seraphs still physically attack like crap, but in the back row they get two full-screen (admittedly still low-to-mid-damaging) holy attacks per battle.

Of course, for the exploitative type, one could also just abuse the Organize Screen's bug that lets you get infinite copies of any item a unit can carry.