Mishka is a nickname for the (female) bear in Rise of the Tomb Raider, given to it by the developing staff and the Ambassadors at the 2015 E3 event. Please note, that this name is not official like it was for FeeFee, the crab on the beach in Tomb Raider (2013). It was assigned as a joke.
Rise of the Tomb Raider
In the course of the game Lara meets the bear at least twice: The first encounter is very early in the beginning of Siberia after she has lost her gear in the avalanche. She can not really defend herself from it so the only option is flight, although she injures it with her Axe.