The Mesec resembles a human-sized crow in appearance and has the ability to fly and chase after their prey. Its behavior is similar to a common crow however, it possesses a greater intelligence than most mutations, choosing to attack its victims when they are distracted by other dangers. Its main venue of attack is to grab its victim and after reaching a certain height, drop them, which causes moderate damage. A Mesec will also try to rake opponents with its razor sharp talons. Mesec are a very rare mutation, only emerging from specific chrysalids during Jake and Sherry's search for the data files in the Edonian mountains, although Neo-Umbrella J'avo occasionally transform into them. The Mesec' head, strangely, is positioned upside down.
For some reason, the Mesec are vulnerable to flash grenades. Simply blinding them with a flash grenade is enough to instantly kill them, likely because the bright UV light emitted from the grenade causes the creature to lose flight balance, immediately killing them once they crashed to the ground.