So, i'm at the tree of life, my team gets pwned yet again with out getting Irenicus to barely injured, due to all his protections. there has to be a better way I found it
the pre-requisite is being able to cast 1 level 9 spell not all to hard
go shape-change............ no not cheesy mind-flayer............ Iron Golem.
I had Nalia shapechange into that beast, and she tanked all of Irenicus' worst spells and suffered no dmg. In the end the poor guy was standing there casting some kind of low level ice spell. once he wastes all his spells on the golem well my paladin ran up to him and 1 greater whrildwind sent him to hell. 1 round ko
hope this helps anybody who had trouble with him, I know I did