What is darkhold iso 8?

Darkhold ISO-8 is a type of upgrade material used in the mobile game Marvel Contest of Champions. This ISO-8 is unique because it has a chance to apply a debuff to the opponent when the player performs a critical hit. The debuff usually varies and includes effects such as stun, incinerate, bleed, shock, and more. The potency of the debuff increases as the player ranks up their Darkhold ISO-8. Obtaining this ISO-8 requires completing special quests and events or purchasing it through the game's shop.