Necropolitians!

[Inevitability]

Next session, the players will be exploring a vampire's undersea lair. Said vampire is centuries old and has travelled large parts of the world, and I am planning on him having discovered a way to turn people undead with little to no loss of abilities. This is mostly a justified way to have the players fight more kinds of foes. However, I want them to have the ability to undergo said ritual themselves.

Would simply saying 'You're undead now, have fun' be balanced, assuming that prevents most healing magic? Do I need to add additional bonuses/penalties? Or is this a horrible idea that should be taken out back and shot?

[Draken]

Next session, the players will be exploring a vampire's undersea lair. Said vampire is centuries old and has travelled large parts of the world, and I am planning on him having discovered a way to turn people undead with little to no loss of abilities. This is mostly a justified way to have the players fight more kinds of foes. However, I want them to have the ability to undergo said ritual themselves.

Would simply saying 'You're undead now, have fun' be balanced, assuming that prevents most healing magic? Do I need to add additional bonuses/penalties? Or is this a horrible idea that should be taken out back and shot?

Well, really depends on what you do about this undeath.

If you just make them zombies that aren't slow and stupid (Undead: Don't have to eat, sleep, breathe. Immune to Poison and Poisoned, Darkvision 60', done). I would just have it cost some money for the ritual and be done with. Maybe pricier if it went the skeleton way and also made it give exhaustion immunity.

Nothing much more special than that.

As for healing. Probably have the locals offer a spell for the job at a cost? Amusingly enough, Goodberry works on undead.

[Tenmujiin]

I'd either have it halve healing or cost an attunement slot. (and give the benifits taht draken listed)

[Talyn]

Cutting healing in half is actually giving them too much of a break. Almost every healing spell and ability in the book says "does not work on undead or constructs" - Goodberry, as mentioned earlier, one of the few exceptions. If you are turning yourself undead, you are forgoing almost all magical healing. Better use those Hit Dice carefully!

The advantages of being free-willed, sentient undead are still pretty overwhelming.

[ImSAMazing]

Next session, the players will be exploring a vampire's undersea lair. Said vampire is centuries old and has travelled large parts of the world, and I am planning on him having discovered a way to turn people undead with little to no loss of abilities. This is mostly a justified way to have the players fight more kinds of foes. However, I want them to have the ability to undergo said ritual themselves.

Would simply saying 'You're undead now, have fun' be balanced, assuming that prevents most healing magic? Do I need to add additional bonuses/penalties? Or is this a horrible idea that should be taken out back and shot?

I think if you give the following treats it will be balanced:
- You don't have to eat, sleep, breathe
- Immunity to poison and being poisoned.
- Character counts as Undead for the purpose of spells.

I think it will be fun!

[Naanomi]

Any Oathbreakers (or potential Oathbreakers) in your party will have the potential of upping party melee damage with their aura by a significant amount if there is a cheap, relatively drawback free way of becoming undead.

[ChubbyRain]

Skeleton Frenzy Berserker Barbarian... Yes.