One is like, really generic so I’m just going to throw a dart.
溟界 Meikai (Abhyss)
Note: 溟 here seems to just be a more obscure spelling of 冥 (Underworld, Darkness, The Abyss, Gloom) combined with 氵, a Kanji radical that refers to something wet or watery. So the imagery is “Somewhere cold, wet and dark”.
I tossed a dart to go with Abyss + Hiss based on the premise this is apparently a Reptile theme based on the TCG. And the Abyss is a valid location in the Ocean, which this Kanji can refer to.
The other suggestion that comes to mind is “Abyssea”.
ドレミコード Doremicode (or Doremichord)
Just a reiteration that Doremicode manipulates the Pendulum Scale, while Abhyss manipulates the Graveyeard.