Quote Originally Posted by Veldraneofsengir View Post
One note: i believe that the vicious rend ability, would require either a bonus action or an incidental to activate, since it activates on the drop bear's turn. A reaction is used when not on your turn.
Most of the time but not always

Quote Originally Posted by 5E SRD
Reactions
Certain special abilities, spells, and situations allow you to take a special action called a reaction. A reaction is an instant response to a trigger of some kind, which can occur on your turn or on someone else’s.