NessVJMP-JP221 Maryuushou Diabolica / Diabolica, Dragon Fiend Commander
Fiend/Effect, DARK, Lv 8, ATK 2300, DEF 0
A Fiend-Type monster whose true power can be unleashed both in the hand and Graveyard!
Further blurbing elaborates that she is designed to synergize with Devil's Gate R and has 2 effects related to Fiend-Type monsters.
As the monster somewhat thematically resembles Diabolos, "Diabolica, Commander of the Dragon Fiends" also seems possible as an alternative localization.