Exon, Sky Ravager

Reach, Shroud
{3} Destroy a minion and gain attack equal to its toughness, discard three cards. If you cannot discard, take five damage.
{10} {t} Gain +2/+2. This doubles every time you cast it.
{r}{r}{r} Gain Double Strike and lose -1/-1. Can only be cast once.
{8} Kill this creature and summon a Wurm with 6/6 with Haste, Double Strike and Lifelink.