Amphibious. Yognak can breathe air and water.

Multiattack. Yognak makes two attacks: one with its bite and one with its tail.

Bite. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 15 (2d10 + 4) piercing damage plus 4 (1d8) poison damage. And the target is grappled (escape DC 13). Until this grapple ends, the target is restrained, and Yognak can’t bite another target.

Tail. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) bludgeoning damage.

Acid Breath (Recharge 5–6). Yognak exhales acid in a 20-foot line that is 5 feet wide. Each creature in that line must make a DC 15 Dexterity saving throw, taking 49 (11d8) acid damage on a failed save, or half as much damage on a successful one.