Cannot be Normal Summoned, unless you control a "Ghostrick" monster. Once per turn: You can change this card to face-down Defense Position. While this card is face-up on the field, 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.
Since “Ghostrick” monsters are relatively weak in terms of ATK and DEF, they would require a substantial amount of support to keep them alive on the field. Mirror wall is not really helpful here since the current meta usually involves high ATK monsters that can hit through your Mirror Wall if you are playing “Ghostrick” themed monsters.
Changes Battle Positions / Flips itself face-down
Cannot Normal Summon / Allows multiple Normal Summons / Prevents your Special Summons
can ghost trick mummy summon many dark monsters in one turn because in card it says you can special summon dark monsters