Khalif Relentless

When Khalif Relentless enters the battlefield, you
get your choice of a speed or longevity counter.
If you have a speed counter, the first red instant
spell you cast from your hand each turn gains
rebound.
If you have a longevity counter, once each turn
you may cast a black sorcery from your graveyard
as though it had flashback. Its flashback cost is
equal to its mana value