Alpha Fish 2014
CR 3 beast
Large beast, unaligned
When it has half its hit points or fewer, the alpha fish can make one headbutt attack as a bonus action.
When the alpha fish uses its Fin Flare, it looks one size category larger than it actually is to any creature that can see it until the start of its next turn.
The alpha fish attacks anything it thinks is threatening, even inanimate objects or illusions. It automatically fails ability checks and saving throws to detect or see through illusions.
The fish can breathe only under water.
Actions
The alpha fish uses its Fin Flare. It then makes two headbutt attacks.
Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) bludgeoning damage.
The alpha fish flares its fins in an attempt to frighten its opponents. Each creature within 30 feet that can see the fish must succeed on a DC 13 Wisdom saving throw or be frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the alpha fish's Fin Flare for the next 24 hours.
Source: Tome of Beasts 2 (Kobold Press) · License: OPEN GAME LICENSE Version 1.0a details