Black Flame-Thunder

Black Flame-Thunder (黒炎雷) is an Intrinsic Skill that belongs to Demon Slimes and was acquired by Rimuru Tempest during his Harvest Festival.

Functions
It merges the effects of the Extra Skills Black Flame and Black Thunder. Though sacrificed to create Uriel, its effects can be recreated through its successor's Law Manipulation power.

Trivia

 * Before the anime adaptation debuting this skill, in That Time I Got Reincarnated as a Slime: Isekai Memories during the 1st Anniversary opening animation, Rimuru uses this skill against Izis.