Wiz18 Lich vs. four 12th level characters

[clark411]

Assuming homefield advantage, and assuming he knows they're coming, and he's not played under his Int rating, I'd say the Lich will pick the party apart unless they have some really wonky spells or feat combinations.

 

[Warbringer]

I'd say its about a 50/50 with the party either depleted at the end of the battle, with 1 or 2 deaths, or completely dead.

Lich CR=18+2 - 4 for no gear (maybe -3) = CR 16 (17)
Party fully equipped CR 12 The party can take on a CR12 using 25% of resources. It can take on 4 CR12 encounters; equivalent CR 16.

16 vs 16 (17)

However, the party is a little under so you are looking at a 15 vs 16 (or17).

50/50ish in favor of the lich.

I'd go 16th level max, and stay away from 9th level spells