I couldn't finish 'em. Looks like this's gonna get complicated.
Dark Grenade is an enemy from Final Fantasy IV: The After Years. It is not a difficult foe to defeat, but avoid using any Fire-elemental abilities on it as that will provoke it to use Self-Destruct on a random party member. If the player wishes for a quick victory against a Dark Grenade and cannot defeat it with their current party, using a Lightning-elemental attack on it will make it use Chain Reaction, destroying it and all of its allies.
A stronger version appears in the PSP release, summoned by Giant's Chest during the battle with Lost Babil. This version comes with far more HP and stats than the original, and can also inflict Blind to the party through the use of the Ninjutsu ability Flash.