Eel Hound

Amphibious. The eel hound can breathe air and water.

Pack Tactics. The eel hound has advantage on an attack roll against a creature if at least one of the hound's allies is within 5 feet of the creature and the ally isn't incapacitated.

Slick Spittle. By spending 2 rounds dribbling spittle on an area, an eel hound can cover a 5-foot square with its slippery saliva. This area is treated as if under the effects of a grease spell, but it lasts for 1 hour.

Slithering Bite. A creature an eel hound attacks can't make opportunity attacks against it until the start of the creature's next turn.

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) piercing damage, and the target is grappled (escape DC 14).