Armored Titan (Anime)

The Armored Titan (鎧の巨人) is an evidently intelligent Titan and an elusive threat to the human race. It first appeared five years ago during the fall of Wall Maria, but it has not returned since.

The Fall of Shiganshina arc
The Armored Titan first appears in the year 845, shortly after the Colossus Titan first breaches Wall Maria, participating in the attack on Shiganshina district. During the chaos of the initial breach, it enters the city and makes his way across the streets to the interior gate. Once there, it charges towards the gate and smashes through it, allowing Titans to invade Wall Maria. It has not appeared again since that day.