Based on the Riddle of the Sphinx: "Which creature has one voice and yet becomes four-footed and two-footed and three-footed?"
Starting at level 16. Evolves when leveled up during the night.
Fake Tears (Dark) Feigns crying to sharply lower the foe's Sp. Def.
Dream Eater (Psychic) Steals HP from a sleeping victim.
Hypnosis (Psychic) May put the foe to sleep.
Rest (Psychic) Sleep for 2 turns to fully recover.
Twinpsy (Psychic/Dark)
Starting at level 50. Has to be brought back with a reviving item after fainting to evolve.
Bite (Dark) An attack that may cause flinching.
Psybeam (Psychic) An attack that may confuse the foe.
Calm Mind (Psychic) Raises Sp. Atk and Sp. Def by focusing the mind.
Self-Destruct (Normal) Powerful but makes the user faint.
Ozlord (Psychic/Dark)
Crunch (Dark) An attack that may lower Spcl.Def.
Future Sight (Psychic) An attack that hits on 3rd turn.
Mirror Coat (Psychic) Counters a Spcl. Atk. move double.
Destiny Bond (Ghost) The foe faints if the user does.
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Weekly Challenge: It's evolving II
Oh, look at these cuties - Twinpsy hits that exact sweet spot between cute and menacing that the best Pokemon designs have, imo.