The Gates of Dark World

When The Gates of Dark World enter the battlefield declare a colour. Demon creatures of the chosen colour gain +1/+1. Instants and Sorceries of the chosen colour cost {1} less to cast from your hand.
The cycle of Darkness - {t} Exile target Demon in your graveyard, then discard 1 Demon creature and draw 1 card. If you control your commander untap The Gates of Dark World afterwards.