User blog comment:Deedlit11/Googology in Magic: the Gathering/@comment-5982810-20130601162657

Russell Jones has recently expanded his combo to 2-->34-->221 damage! The key to these large values seems to be that each card effect, when stacked with all previous card effects, allows for one additional layer of primitive recursion (the equivalent of adding one up-arrow). Somehow Russell has managed to get more than 60 primitive recursions out of a 60 card deck!

Russell also goes on to say that Magic currently has no use for Chain arrows beyond 3 arguments. I figure this means that Magic currently has limit ordinal w. Ridiculous in a card game, but really small for googology.