Black Ursa

Black Ursas are hostile melee mobs that spawns in the Mega Taiga Biome of the Overworld. They take up a 2x2x2 area.

Behavior
The Black Ursa uses melee attacks, causally walking up to the player and attacking. It has an enormous range, however, as they often start chasing player who are up to 50 blocks away.

Tips
If you first spawn in a mega taiga, you're gonna have a tough time with the mob because Black Ursas spawn fairly commonly and sometimes are immune to knockback when you hit them. Trying to get to a safe place and hitting them is your best option, but be careful, because if there are two or more after you, one of them could get behind the other and give the one in front the advantage of hitting you, and that's never a fun time. They do drop Raw Ursa though, which is not really worth it, as it's only as good as apples when it's cooked. Ranged damage is also a great option, just watch what's behind you.

Trivia

 * To spawn this mob, you must just type in "Ursa" instead of its given name, "Black Ursa."
 * Sometimes it will get stuck when it it supposed to jump. It also sometimes goes toward you as its body is facing diagonally, or even sideways from you.
 * It has no hit-box at the end of its muzzle, or the tip of its tail.
 * Unlike most other mobs, the Black Ursa walks by swinging all four of its legs in the same direction instead of alternating them (possibly a bug).

References/Sources
http://adventofascension.gamepedia.com/Black_Ursa