I wonder if the YCS Darklords Sweepstakes has anything to do with this.
Kyouraku no Datenshi / Darklord of Delight
Level 4 DARK Fairy Effect Monster
You can use each effect among the (1)st and (2)nd effects with this card’s name only once per turn.
(1) During any Main Phase, you can (Quick Effect): Immediately after this effect resolves, Tribute Summon 1 Fairy monster face-up.
(2) If this card is sent to the GY: You can make all face-up monsters your opponent currently controls lose 500 ATK/DEF for each Fairy monster currently on the field, until the end of this turn.
Etsuraku no Datenshi / Darklord of Pleasure
Level4 DARK Fairy Effect Monster
You can use the [(1)st] effect with this card’s name only once per turn.
(1) If this card is Normal or Special Summoned: You can activate this effect; for the rest of the turn, you cannot activate monster effects, except Fairy monsters’ effects, also choose 2 “Darklord” monsters in your hand and/or Deck that have different Levels, and if you do, Special Summon 1 of them to your opponent’s field in Defense Position, and if you do that, add the other to your hand.
Datenshi Nergal / Darklord Nergal
Level 8 DARK Fairy Effect Monster
You can Special Summon “Darklord Nergal(s)” only once per turn.
You can use the (2)nd effect with this card’s name only once per turn.
(1) If your Fairy monster attacks a Defense Position monster, inflict piercing battle damage to your opponent.
(2) (Quick Effect): You can pay 1000 LP, then target 1 “Darklord” Spell/Trap in your GY; apply that target’s effect, then shuffle that target into the Deck.
Reimei no Datenshi Lucifer / Lucifer, Darklord of the Morning Star
Level 12 DARK Fairy Fusion Effect Monster
Fusion Materials: 3 DARK Fairy monsters
You can use only one effect among the (1)st and (3)rd effects with this card’s name per turn, and only once that turn.
(1) If this card is Fusion Summoned using “Darklord Morningstar” as material: You can destroy all cards your opponent controls.
(2) Fairy monsters you control cannot be targeted by your opponent’s card effects.
(3) During any Main Phase (Quick Effect): You can pay 1000 LP; Special Summon 1 Fairy monster from your hand or GY in Defense Position.
ROTD-JP075 Hangyaku no Dantenshi / Rebellious Darklord
You can only activate 1 card with this card’s name per turn.
(1) Send 1 “Darklord” monster that is in your hand or face-up on your field to the GY; Fusion Summon 1 DARK Fusion Monster from your Extra Deck, using monsters from your hand and/or field as Fusion Material, then you can gain LP equal to the ATK of the monster sent to the GY to activate this card (its ATK on the field, if sent from there).