Amphibious. Yashagoglex can breathe air and water.

Speak with Frogs and Toads. Yashagoglex can communicate simple concepts to frogs and toads when it speaks in Bullywug.

Swamp Camouflage. Yashagoglex has advantage on Dexterity (Stealth) checks made to hide in swampy terrain.

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

Legendary Resistance (3/Day). If Yashagoglex fails a saving throw, he can choose to succeed instead.

Spellcasting. Yashagoglex is a 20th-level spellcaster. It's spellcasting ability is Intelligence (spell save DC 16, +8 to hit with spell attacks). Yashagoglex has the following wizard spells prepared:

Cantrips (at will): fire bolt, mage hand, poison spray, minor illusion

1st level (4 slots): disguise self, [Tooltip Not Found], silent image, fog cloud, distort value

2nd level (3 slots): mirror image, invisibility, hold person

3rd level (3 slots): remove curse, fireball, vampiric touch

4th level (1 slot): storm sphere

Evasion. If Yashagoglex is subjected to an effect that allows it to make a Dexterity saving throw to take only half damage, Yashagoglex instead takes no damage if it succeeds on the saving throw, and only half damage if it fails.

Sneak Attack. Once per turn, Yashagoglex deals an extra 33 (10d6) damage when it hits a target with a weapon attack and has advantage on the attack roll, or when the target is within 5 feet of an ally of Yashagoglex that isn't incapacitated and Yashagoglex doesn't have disadvantage on the attack roll.

Mage Hand Legerdemain. When Yashagoglex casts mage hand, he can make the spectral hand invisible, and he can perform the following additional tasks with it:

• Yashagoglex can stow one object the hand is holding in a container worn or carried by another creature.
• Yashagoglexcan retrieve an object in a container worn or carried by another creature.
• Yashagoglex can use thieves’ tools to pick locks and disarm traps at range.

Yashagoglex can perform one of these tasks without being noticed by a creature if he succeeds on a Dexterity (Sleight of Hand) check contested by the creature’s Wisdom (Perception) check.

In addition, Yashagoglex can use the bonus action granted by his Cunning Action to control the hand.

Magical Ambush. if Yashagoglex is hidden from a creature when he casts a spell on it, the creature has disadvantage on any saving throw it makes against the spell this turn.

Reliable Talent. Whenever Yashagoglex makes an ability check that lets him add his proficiency bonus, he can treat a d20 roll of 9 or lower as a 10.

Elusive. No attack rolls can have advantage against Yashagoglex while he isn’t incapacitated.

Multiattack. The bullywug makes two melee attacks.

Shortsword. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) piercing damage.

Cunning Action. as a bonus action on each of Yashagoglex turns in combat. This action can be used only to take the Dash, Disengage, or Hide action.

Versatile Trickster. As a bonus action Yashagoglex can designate a creature within 5 feet of the spectral hand created by the spell. Doing so gives him advantage on attack rolls against that creature until the end of the turn.

Spell Thief (Recharges after a long rest). Immediately after a creature casts a spell that targets himself or includes Yashagoglex in its area of effect, Yashagoglex can use his reaction to force the creature to make a saving throw with its spellcasting ability modifier, DC 16. On a failed save, Yashagoglex negates the spell’s effect against and steals the knowledge of the spell if it is at least 1st level and of a level that Yashagoglex can cast (it doesn’t need to be a wizard spell). For the next 8 hours, Yashagoglex knows the spell and can cast it using his spell slots. The creature can’t cast that spell until the 8 hours have passed.

Stroke of Luck (Recharges after a short or long rest). If Yashagoglex's attack misses a target within range, he can turn the miss into a hit. Alternatively, if Yashagoglex fails an ability check, he can treat the d20 roll as a 20.

Yashagoglex can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. Yashagoglex regains spent legendary actions at the start of his turn.

Toad Summoning. Yashagoglex magically summons a giant toad in an unoccupied space within 10 feet of himself. The toad is loyal to Yashagoglex and obeys his orders given to him in bullywug from Yashagoglex and can also speak bullywug.

Swamp of The Underworld (Costs 2 actions). Yashagoglex transforms the area around one creature he can see and turns the ground beneath it into mud as if by the effects of the transmute rock spell. The mud is 10 feet deep.

Sage Mode (Costs 3 actions). Yashagoglex becomes under the effects of the guardian of nature spell. Yashagoglex chooses which effect of the spell to be under each time this action is used and cannot be used again until it's effect has ended.