Armin Arlert

The strategist who inherited the Colossal Titan.

Armin Arlert is Eren's and Mikasa's other childhood friend. His parents tried to venture beyond the Wall in a hot air balloon but were found out and killed by the First Interior Squad of the Military Police, leaving Armin to be raised by his grandfather, whose illegal book about the world beyond the Walls kindled Armin's and Eren's desire to see the outside world. After joining the Training Corps, Armin realized he could use his brain and strategic abilities to help his companions.

Quick Facts

Titan: Colossal Titan (from Bertolt)
Rank: 15th commander of the Survey Corps

Facts from the source article.

Background

During a battle in Shiganshina, Armin comes up with a plan to capture Bertolt but is mortally wounded from the severe burns he sustained. Levi saves Armin by injecting him with Titan serum instead of Erwin, and Armin then acquires the Colossal Titan's power by eating Bertolt.

After initially struggling with survivor's guilt, he joins the alliance to stop Eren from destroying all life outside Paradis, and later, after Hange's death, became the 15th commander of the Survey Corps. During the battle of Heaven and Earth, he was devoured by an Okapi Titan and entered the Paths, where he convinced Zeke to surrender his life to stop the Rumbling.