I'm running a homebrew campaign for a party of 10 players in DnD 5e (bard, druid, rogue x2, paladin x3, warlock, monk, cleric). I'm planning for a lich to be one of the major encounters before they enter a different setting. I know the guidelines for creating encounters, but I have no idea what to expect with so many turns against one enemy. I'm open to adding other enemies to the encounter in order to balance things out. Hoping for the encounter to be hard, but not deadly. Splitting the party isn't an option here either. Thoughts?
According to the Encounter Builder, your player characters would only need to be around 8th or 9th level for a single Lich to be considered a "hard" encounter.
Having so many PCs skews the balance quite considerably and such an encounter wouldn't work very well using the monster as-is. This is because a lich has access to high-level spells that would mean instant death to any 8th or 9th level character. E.g. Disintegrate, Finger of Death, Power word kill....
It would end up depending entirely on initiative: If most of your players go first, they could kill the lich before it even had a chance to do anything. If the lich goes early in the initiative, it will kill at least 1 character immediately (maybe more with Cloudkill).
- Use a few lower-level minions to balance out the action economy (though with so many players you don't want too many or the combat could become a slog).
- Nerf the lich by replacing the high-level instant death spells with some lower level spells or simply use a lower-level undead if you have access to them (can still call it a 'lich' in-game). Examples include the Skull Lord, Eldritch Lich, Deathlock Mastermind etc.
If we do this according to the DMG, then:
- A lich is CR 21 and is worth 33000xp.
- I told Kobold Fight Club that I had ten player characters, and I adjusted their level until 33000xp was a "hard" but not "deadly" encounter. This gave me level 11.
- By contrast, if I only have five player characters, then they need to be level 16 for 33000xp to be a "hard" but not "deadly" encounter.
The rules were designed for groups of five player characters, so I feel mistrustful about the result describing ten level-11 characters fighting a single lich. If I were balancing the battle, I would feel more comfortable pitting two liches against ten level-16 characters.
Liches may not be the best opponents because they sometimes use magic that directly kills characters, such as disintegrate or power word kill. This might not be fun for the player whose character is killed. Consider replacing these spells with spells that will be more fun for the group to interact with.