This is a tip for druid and cleric characters to kill belial (you don't need to). it takes long but is relatively easy: just memorize slay living and save just after summoning belial. cast slay living on him. his sr is 28 which you can beat with 20+caster lvl. if you are lvl 9 (which is required to cast lvl 5 spells), you just need to load and try to roll 20. his fortitude save is low. but protection from elements would be handy as he blows up when killed (up to 70 fire damage).