Resurrection, reincarnation, raise dead. Do not function. The world has never seen someone brought back to life. This is generally of little concern to players since player death is rarely planned out with plans of later resurrection. This is mostly to prevent storyline and lore hiccoughs of “But, why doesn’t the BBEG who’s a 20th level cleric just continually true res his most powerful minion” or “why doesn’t this altruistic and lawful good monastery just keep on resurrecting those who die in accidents?” You can come up with patchwork excuses for why, but I don’t really think it’s a necessary spell in the game and it’s absence could create a grittier atmosphere where one wrong move means permanent death.
Undead. In the same line, this isn’t going to be an undead heavy campaign. There have been myths and legends, but no reliable sources have indicated the dead walk. The magic users of the party will have heard of attempts to bring back the living, either a resurrection attempt or to create undead minions, but these attempts create horrible abominations that the caster has no control over. They’re mindless and incapable of concerted movement, their eyes empty and faces pained. As such, experimentation in these vile arts are forbidden by every civilized society you’ve ever heard of. There currently aren’t any raise undead spells anyways.