If you have no card in your Field Card Zone and all face-up monsters you control (min. 1) are Zombie-Type: Activate 1 "Vampire Kingdom" directly from your Deck, then, you can Special Summon 1 DARK "Vampire" monster from your Graveyard in face-up Defense Position. You can only activate 1 "Vampire Takeover" per turn.
Revived Vampire monster is summoned in defense position.
Can only be activated if you control a Zombie-type monster.
You can activate Vampire Takeover even if you have no Vampire monsters in the grave to revive.
Your field card zone must be empty and you must control a face-up Zombie-type monster to use Vampire Takeover
Here are the monsters you can revive with Vampire Takeover. Vampire Familiar and Vampire Retainer searches your deck for a Vampire monster or Vampire Spell/Trap card respectively when they are special summoned from the graveyard. Vampire Scarlet Scourge will allow you to revive another Vampire monster when he is special summoned. And if you special a level 5 or higher Vampire monster with Vampire Takeover, Vampire Grace can be revived from the graveyard with her own effect.