Changeling Hulk

Shapechanger. The changeling hulk can use its action to polymorph into a Large or Medium humanoids and giants with Challenge ratings 4 or less that the changeling hulk has seen, or back into its true form. Its statistics, other than its size, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Amorphous. The changeling hulk can move through a space as narrow as 3 feet wide without squeezing.

Spider Climb. The changeling hulk can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Ambusher. The changeling hulk has advantage on attack rolls against any creature it has surprised.

Surprise Attack. If the changeling hulk surprises a creature and hits it with an attack during the first round of combat, the target takes an extra 10 (3d6) damage from the attack.

Multiattack. The changeling hulk makes two melee attacks.

Slam. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) bludgeoning damage.

Read Thoughts. The changeling hulk magically reads the surface thoughts of one creature within 60 feet of it. The effect can penetrate barriers, but 3 feet of wood or dirt, 2 feet of stone, 2 inches of metal, or a thin sheet of lead blocks it. While the target is in range, the changeling hulk can continue reading its thoughts, as long as the changeling hulk's concentration isn't broken (as if concentrating on a spell). While reading the target's mind, the changeling hulk has advantage on Wisdom (Insight) and Charisma (Deception, Intimidation, and Persuasion) checks against the target.