Shapechanger. The Yuanganger can shapeshift between a snake, a human it has seen, or its true form, a creature resembling a doppelganger with purple scales.

Surprise Attack. If the Yuanganger 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.

Magic Resistance. The Yuanganger has advantage on saving throws against spells and other magical effects.

Multiattack. Can slam and bite in one round.

Slam. Melee Weapon Attack: +6 to hit, reach 6 ft., 1 target. Hit: 35 (7d6 + 10) bludgeoning damage. 

Bite. Melee Weapon Attack: +6 to hit, reach 3 ft., 1 target. Hit: 4 (1d4 + 2) piercing damage.

Read Thoughts. The Yuanganger 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 doppelganger can continue reading its thoughts, as long as the doppelganger's concentration isn't broken (as if concentrating on a spell). While reading the target's mind, the doppelganger has advantage on Wisdom (Insight) and Charisma (Deception, Intimidation, and Persuasion) checks against the target.