Relentlessly Territorial. This terrifying creature possesses a cunning and devious mind which it uses to bend others to its will. The devil shark considers itself superior to all other creatures of the sea and goes to great lengths to prove it. A merciless, vicious predator when active, a devil shark carves out and defends a territory for itself measured in leagues, relentlessly hunting down any creature it considers a competitor for primacy.

Slumbering Evil. The creature relies in part on the terror it spreads during its periods of activity to keep it safe and undisturbed during its long periods of dormancy. While dormant, it sleeps in deep undersea caves or ancient submerged structures of unknown artifice.

Object of Veneration. The devil shark is a solitary creature, though it sometimes enjoys the worship of sahuagin. As rapacious as the hungriest shark, the devil shark enjoys consuming the flesh of sentient creatures and looks kindly on those providing it with such sacrifices, though it will just as soon eat those same admirers should such offerings cease.

Alternate Traits and Actions

Source ExpCod (Open Design)

The following changes allow GMs to alter a devil shark without modifying its challenge rating.

Amphibious. The devil shark can breathe air and water. It also has a speed of 10 feet. The devil shark loses its Water Breathing trait. Additionally, its swim speed is reduced to 40 feet.

Crushing Charge. If the devil shark swims at least 20 feet straight toward a creature and hits with a slam attack on the same turn, the target takes an additional 22 (4d10) bludgeoning damage and must succeed on a DC 18 Strength saving throw or be knocked 20 feet away from the devil shark. The devil shark gains a slam melee weapon attack, and its bite attack is modified:

Bite. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 24 (3d10 + 7) piercing damage and the target is grappled (escape DC 18).

Slam. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 18 (2d10 + 7) bludgeoning damage.

Icy Belly. A creature swallowed by the devil shark takes 10 (3d6) acid damage and 10 (3d6) cold damage at the start of each of the devil shark's turns. This trait modifies the devil shark's Swallow action.

Summon Giant Shark (1/Day). The devil shark summons 1d4 sharks. A summoned shark appears in an unoccupied space within 60 feet of the devil shark, acts as an ally, and remains for 1 minute. The devil shark loses its Magic Resistance trait when it gains the Summon Giant Shark action.

Vortex (Recharge 4-6). The devil shark creates a vortex of water within 30 feet of it that lasts for 1 minute. The vortex is 5 feet in diameter and up to 30 feet tall. A creature occupying the space where the vortex appears or entering the vortex for the first time on a turn must make a DC 18 Dexterity save or be restrained and take 2d8 bludgeoning damage. As an action, a creature can free itself or another creature from a vortex by succeeding on a DC 18 Strength check. The devil shark loses its Freezing Breath action.