Spell and Trap Assassins

The Spell and Trap Assassins are a group of DARK Warrior-Type monsters that can be Special Summoned by sending one or more Spell or Trap Cards from the field to the Graveyard. Either player's cards can be used to Summon them, but depending on whose card is sent, the Assassins gain either beneficial effects or an effect that makes them a liability and a drain on their controller's Graveyard. Their effects mainly revolve around removing Spell and Trap Cards in your Graveyard for cost.

Playing Style
The Assassins are not numerous enough to have a Deck built purely around them. Indeed, they will be used as Special Summon support for standard Warrior Decks, usually as quick beatsticks or for the Synchro Summoning of the "Warrior" Synchro monsters.

The Spell and Trap Assassins' main advantage is their ability to potentially turn a dead draw into an advantage. An unusable Spell or Trap can be Set, then destroyed to Summon one of the Assassins, in turn possibly being removed from play to activate the summoned monster's effect. Their Levels also mean they can be used to set up Synchro Summons, with their cost being fulfilled with your opponent's cards. Their negative effects almost completely rule out keeping them on the field, unless used as an emergency defense or with cards like "Creature Swap" or "Share the Pain".

Weaknesses
Despite needing a field sacrifice to be Summoned, the Spell and Trap Assassins' effects mainly focus on removing cards in your Graveyard to deplete your opponent's Graveyard and Deck. Also, if Normal Summoned, they have no effects and have average or low ATK and DEF for their Level. Their biggest weakness is that they cannot be Special Summoned, except by their own effects, rendering cards like "Call of the Haunted" and "The Shallow Grave" useless.