Avernus Gate

Avernus Gate enters the battlefield tapped.
Hexproof You cannot gain life
{t} add {r}{b} Spend this mana only to cast a Demon, Devil or Imp spell
or to activate an ability of a Demon, Devil or Imp.
Demon spells cost {1} less to cast & Demon's you control gain Swampwalk.
Devil's you control gain +1/+1
Imps you control gain Haste & Mountainwalk