Acnologia — better known as The Black Dragon of the Apocalypse — is basically the most terrifying force in the Fairy Tail world. This dragon roams across the continent and is stupidly overpowered; it once fought Gildarts, Fairy Tail's strongest mage, and destroyed him in seconds, literally tearing out his organs. That's the kind of power we're talking about.
What's wild is that even Zeref, the most evil and powerful mage alive, is genuinely afraid of Acnologia. These two clearly have some kind of connection — Zeref knows it intimately and can sense when it's coming from miles away. He's described Acnologia as something that "Heralds the End of Eras," though fans are still trying to figure out exactly what that means.
Content compiled by AnimeList.moe from publicly available sources.
