Fenrirborn's Full-Morph (5e Creature)
From D&D Wiki
Large beast, unaligned
Pack Tactics. The wolf has advantage on an attack roll against a creature if at least one of the wolf's allies is within 5 feet of the creature and the ally isn't incapacitated.
The form a fenrirborn may take whenever they please. This form is an outrageously powerful one that boost their fighting capabilities. This form is that of a dire wolf (A fenrirborn may take on these stats if they're overall stats are lower than this creature's)