Ghostrick Mummy (LVAL-EN025) [Legacy of the Valiant]

Cannot be Normal Summoned, unless you control a "Ghostrick" monster. Once per turn: You can change this card to face-down Defense Position. During your Main Phase, you can Normal Summon 1 "Ghostrick" monster in addition to your Normal Summon/Set. (You can only gain this effect once per turn.) You cannot Special Summon any monsters, except DARK monsters.