Xarnek, Looter of the Deepths

Whenever one or more cards leave your graveyard,
you get an experience counter.
Spells you cast have "As an additional cost to cast
this spell, you may exile up to X cards from your graveyard, where X is equal to how many
experience counters you have. This spell costs {1} less to cast for each card exiled this way."
"What is buried in the deep doesn't necessarily stay
there."