MVP card is 100% when using Silit Pong so yeah, should work on a Fenrir carded in a helm.. If tis mid then too bad, can't uncard it.
Though, what is considered as in the newer MvP card list.
I'm aware of this since Fenrir is not considered as mvp. If you right click on some mvp cards, it has mvp written on it and Fenrir Card does not have it.