Malazan Empire: icarium - Malazan Empire

i havent read DHG in ages and I was just wondering how exactly is icarium so powerful, is it in his blood etc?

he seems to be on a par with Rake, Brood etc.

this is confusing because it was always fairly implicit that rake could have seen off raest even if raest had got his finnest. And Raest was regarded as one of the most powerful of the jaghut.