Mon3tr | Arknights

Originally appearing as a crystaline, green, dragon-like monster, Mon3tr (pronounced "monstr" or "monztr") is a biomechanical creature of unknown origin related to Kal'tsit and always seen together with her which possesses a highly durable, likely metallic skin, which makes it immune to most conventional weaponry. Its sheer strength also allows Mon3tr to easily cut down even the most hardy of enemies with its razor-sharp talons and could even rival the strength of the dreaded Emperor's Blade. It could also send out fiery beams upon targeting its prey.[1]

Strangest of all, Mon3tr is neither a manifestation of Originium Arts nor a true living creature, but it is certain that it and Kal'tsit has a symbiotic relationship where it understands whatever she says, who often reacts to its actions. In turn, Kal'tsit seems to understand Mon3tr's emotions and could quickly bring it under control. Kal'tsit is never seen fighting herself, instead delegating the task to Mon3tr; therefore, Mon3tr is both her main offensive and defensive option and acts as her proxy in combat.

Outside of combat, Mon3tr assumes the form of a floating octahedral crystal with black and green hues.[note 1] While Crownslayer claims that Mon3tr comes out of Kal'tsit's spine,[2] in reality its crystal form is right behind her which Crownslayer didn't notice due to its compact size, small enough to be obscured by Kal'tsit.

Before it is introduced under a human form as an Operator alongside Episode 15, Mon3tr appears throughout the Main Theme under its monstrous form and as a summoned unit tied to Kal'tsit as an Operator. It is also confirmed to return in Arknights: Endfield as a supporting character whose appearance resembles Kal'tsit herself.