Darkrai GX (139/147) [Sun & Moon: Burning Shadows] ST3-02 you can Synchro Summon using

you can Synchro Summon using this face-up card you control as a Synchro Material Monster

"Red Dragon Archfiend" must be on the field to activate and to resolve this effect

Set: Classic Collection Card type: Digimon Rarity: Common Digi type: Birdkin Play Cost: 6 Form: Ultimate Attribute: Vaccine Digivolve Cost: 3 Digivolve Cost Level: 4 [When Attacking][Once Per Turn] When this Digimon attacks a player

You can only use this effect of "Nekroz Cycle" once per turn

You may digivolve 1 green level 6 Digimon card among them onto the attacking Digimon without paying its memory cost

Darkrai GX (139/147) [Sun & Moon: Burning Shadows] ST3-02 you can Synchro Summon usingSet: Sun & Moon: Burning Shadows Type: Darkness Rarity: Ultra Rare Retreat cost: Colorless,Colorless