Glintstone Dragon Smarag

Flying

Whenever Glintstone Dragon Smarag attacks, draw
a card, then discard a card. Glintstone Dragon
Smarag gets +X/+0 until end of turn, where X is
the discarded cards mana value.

"Smarag was a devourer of sorcerers, and over time,
his body became corrupted by their glintstones."
—Unknown Traveler