It’s time for all those King cards to show up.
Dark Fiend / Tuner / Effect
You can only Special Summon “Synclone Resonator” with its (1) effect once per turn. (1) If there is a Synchro Monster on the field, you can Special Summon this card (from your hand). (2) If this card is sent from the field to the Graveyard: You can target 1 “Resonator” monster in your Graveyard, except “Synclone Resonator”; add it to your hand.
Light Fiend / Tuner / Effect
(1) When this card is Normal Summoned while there is a Synchro Monster on the field: You can Special Summon 1 “Resonator” monster from your Deck, except “Chain Resonator”.
Enmaryuu Red Daemon Belial / Hot Red Dragon Archfiend Belial
Dark Dragon / Synchro / Effect
1 Tuner + 1 non-Tuner DARK Dragon-Type Synchro Monster
You can only use each effect of “Hot Red Dragon Archfiend Belial” once per turn. (1) You can Tribute 1 monster, then target 1 “Red Daemon*” monster in your Graveyard; Special Summon it. (2) When this card inflicts battle damage to your opponent: You can Special Summon 2 Tuners of the same Level (1 from your Deck and 1 from your Graveyard) in Defense Position.
*Red Daemon is included in the names of all monsters the TCG calls “Red Dragon Archfiend”, but it’s entirely possible they might expand this theme to beyond that and have monsters like “Red Daemon Golem” or “Red Daemon Resonator”, so I’m leaving it be for now. But you can think of it as saying “Red Dragon Archfiend” monster right now.