[{quoted}](name=FOR JUSTICE,realm=NA,application-id=RaE1aOE7,discussion-id=UBNlxF7F,comment-id=0000,timestamp=2019-07-20T17:04:11.095+0000)
TFT doesnt use normal league logic. mana is used for pretty much all abilities.
there are some units in TFT that do not build up mana.
vayne and graves dont build up any mana at all, because they have no spells and get passive auto attack amplifiers instead. there is no mana to drain for kassadin to shield himself.
his description says, that kassadins auto attacks drain a units mana, and grant him a shield from the mana drained. it doesnt make sense that he still gets the shield when he attacks a target without mana.