Moving on to 3rd edition OA there are a few new monsters in this book that were not in 1e. Converting them here.
Since these are effectively Asian doppelgängers I built them from the same skeleton to show that they are related. I like that continuity between the mythologies and ecologies in D&D.
Shapechanger. The mamono 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 mamono has advantage on attack rolls against any creature it has surprised.
Rejuvenation. If a mamono is killed at night, it reawakens in 2 hours, completely healed and very angry. The only reliable way to kill a mamono is to cut it into three or more parts and bury them separately. A mamono cannot rejuvenate if killed during the day or exposed to direct sunlight.
Surprise Attack. If the mamono 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.
Innate Spellcasting. The mamono’s spellcasting ability is Charisma (spell save DC 12). It can innately cast the following spells, requiring no material components:
- At will: invisibility
Sunlight Hypersensitivity. The mamono takes 1d8 radiant damage when it starts its turn in sunlight. While in sunlight, it has disadvantage on attack rolls and ability checks.
Multiattack. The mamono makes three arm blade attacks.
Arm Blades. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 4) slashing damage.
Torso Maw. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 4) piercing damage and 5 (2d4) poison damage.
Read Thoughts. The mamono 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 mamono can continue reading its thoughts, as long as the mamono’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.
Mamonos are hideous shapechangers with a strong resem- blance to doppelgangers. In their natural form, they are skin- less creatures of bone and muscle, with a single eye and a gaping, spiderlike maw in their abdomens. Their arms end in serrated blades of bone, each as deadly as a wakizashi.
Like doppelgangers, mamonos use their natural abilities of mimicry and deception to infiltrate human society. Unlike dop- pelgangers, however, they are motivated by a deep loathing of humanity rather than simple self-interest, and they delight in flaying their victims before devouring their eyes, liver, and other soft tissue.
In human form, a mamono attacks with a weapon or unarmed, but if it is severely threatened it reverts to its natural form and uses its formidable natural weaponry.