Doppelganger
Medium Monstrosity (shapechanger), unaligned
700 XP
Special Abilities
Shapechanger
The doppelganger can use its action to polymorph into a Small or Medium humanoid it 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.
Ambusher
The doppelganger has advantage on attack rolls against any creature it has surprised.
Surprise Attack
If the doppelganger 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.
Actions
Multiattack
The doppelganger makes two melee attacks.
Slam
Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 4) bludgeoning damage.
Read Thoughts
The doppelganger magically reads the surface thoughts of one creature within 60 ft. of it. The effect can penetrate barriers, but 3 ft. of wood or dirt, 2 ft. 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.
Quick Reference
Running This Encounter
Doppelgangers are masters of deception and psychological warfare. Use their Read Thoughts ability to exploit party secrets and fears, creating paranoia and mistrust among the group. The real threat comes from their ability to perfectly mimic party members, forcing players to question each other's identities and loyalties. Reveal the doppelganger's presence gradually through inconsistent behavior or impossible knowledge rather than immediately—this heightens tension and makes combat feel like a climactic revelation.
Combat Tactics
Doppelgangers prioritize eliminating the party's trust and support systems before engaging in direct combat. They use their shapeshifting to separate party members, impersonate key figures (healers, leaders), and sow discord through mimicry. In combat, they target spellcasters and support characters first, relying on their decent AC and moderate HP to outlast focused fire while using the confusion of their appearance to gain advantage.
Environment & Setting
Doppelgangers thrive in civilized settings—towns, courts, merchant caravans, and social gatherings where infiltration matters. They work best in encounters with multiple NPCs or crowded locations where the party cannot immediately distinguish the real from the fake.