This forum is format specific rules for Commander. There is a Rulings forum for questions like this. And, when asking rules questions, card tags are mandatory: [c]Rayami, First of the Fallen[/c] = Rayami, First of the Fallen
When cards change zones, they lose whatever counters they have. So, in exile, Crystalline Giant will have none of its counters (it will have the Blood Counter of course) which means it has no abilities for Rayami to get.