Reactor

Reactors are an Archetype from Yu-Gi-Oh! 5D's. They are used by Bommer in the anime. Their effects inflict 800 damage to the opponent, when they play a particular type of card. In the case these monsters except "Summon Reactor AI", the card the opponent played is destroyed when the Reactor's effect resolves. The effect of the destroyed card is not negated, however.

The lettered suffixes of "Summon Reactor SK", "Trap Reactor Y FI", and "Spell Reactor RE" spell out "SKY FIRE". Together they combine to Summon "Flying Fortress SKY FIRE". In the Japanese version, the reactors are called "Summon Reactor AI", "Trap Reactor RR", and "Magic Reactor AID". Their suffixes spell "AIRRAID", while "Flying Fortress SKY FIRE's" name is "Giant Bommer Airraid".

Visually, they are all based off of WWII-Style aircraft, specifically bombardment-type or fighter/bomber aircraft. They were released in the Pack, Crimson Crisis.

The use of Reactors can force an opponent into a difficult situation, especially when multiple different Reactors are on the field. Simply playing cards will cause the opponent to take damage, and the Reactor's effect to destroy the played card will make it much harder for the opponent to use cards that are intended to remain on the field, such as Equip Spell Cards, or Continuous Spells and Traps.