Opportunist. When someone provokes an opportunity attack from this monster, it gets two attacks instead of one.   Stealth Striker. If a creature is surprised, the tiger gets advantage on attack rolls against the creature and any roll that is 19 or above is a critical hit.   Abyssal Potential. These monsters, when summoned as an ally of the summoner and not in a subjugation ritual, their hitdie will increase by an amount equal to (Caster Level - 10), and their damage die will increase by an amount equal to (amount of Ability Score Improvements - 2) they've had.