Amphibious. Thogg can breathe air and water.

Legendary Resistance (1/Day). If Thogg  fails a saving throw, it can choose to succeed instead.

Noxious Fumes. A 15-foot radius around Thogg is filled with poisonous gas. When a creature starts its turn in the aura or enters it for the first time on a turn, it must make a DC 18 Constitution saving throw, taking 14 (4d6) poison damage on a failed save, or half as much damage on a successful one. Creatures that fail their saving throw are also poisoned until the start of their next turn.

Standing Leap. Thogg 's long jump is up to 20 feet and its high jump is up to 10 feet, with or without a running start.

Swampwalk. Thogg can move across difficult terrain made of mud, swamps, or other marshy environments without needing to make an ability check. While in such terrain, Thogg has advantage on Stealth checks.

Tongue Lash. Melee Weapon Attack: +11 to hit, reach 20 ft., one target. Hit: 19 (3d8 + 6) bludgeoning damage. If the target is a creature, it is grappled (escape DC 18). Until this grapple ends, the target is restrained, and Thogg cannot use its Tongue Lash on another target.

Stomp. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 18 (3d6 + 6) bludgeoning damage plus 10 (3d6) acid damage. If this attack hits, the target's speed is reduced by 10 feet until the end of its next turn.

Swallow. The frog makes one bite attack against a Small or smaller target it is grappling. If the attack hits, the target is swallowed, and the grapple ends. The swallowed target is blinded and restrained, it has total cover against attacks and other effects outside the frog, and it takes 5 (2d4) acid damage at the start of each of the frog's turns. The frog can have only one target swallowed at a time. If the frog dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 5 feet of movement, exiting prone.

Ooze Spit (Recharge 5-6). Thogg can spit a blob of corrosive ooze at a target within 60 feet. The target must succeed on a DC 18 Dexterity saving throw or take 27 (6d8) acid damage and be covered in slime. A creature covered in slime takes 10 (3d6) acid damage at the start of each of its turns until it or another creature uses an action to scrape it off. An affected target's speed is halved, it takes a −2 penalty to AC and Dexterity saving throws, and it can't use reactions. On its turn, it can use either an action or a bonus action, not both. Regardless of the creature's abilities or magic items, it can't make more than one melee or ranged attack during its turn.