Mard Geer Tartaros

Mard Geer Tartaros is a major antagonist in Fairy Tail, serving as the founder and de facto leader of the dark guild Tartaros during the Tartaros arc.

He is an Etherious (a powerful demon created by Zeref) and is known by titles such as the Underworld King (冥王 Meiō) and the Definitive Demon (絶対の悪魔 Zettai no Akuma). He acts as the guild's leader in the absence of its nominal master, E.N.D., and views himself as the supreme demon among Zeref's creations.

Personality-wise, Mard Geer is arrogant, calm, highly intelligent (or at least presents himself as such), and often speaks in a sophisticated, condescending manner, frequently referring to himself in the third person while smirking.

His ultimate goal ties into ending Zeref's life (to grant him death), and he wields extremely dangerous curses, including his signature Thorn Bramble (thorny vines) and the devastating Memento Mori (a curse meant to erase existence in darkness).

He's one of the most powerful demons in the series and the primary big bad of the Tartaros storyline.