The sorcerer chanted a spell and defeated the enemy.
The wizard in the story uses dark powers.
魔術師 is similar but can refer to a broader range of magic, including stage magic; 妖術師 emphasizes the sinister or occult aspect.
Compound of 妖術 (yōjutsu, 'black magic, sorcery') + 師 (shi, 'master, practitioner'). The exact historical derivation is uncertain, but the kanji 妖 (bewitching, calamity) and 術 (technique, art) suggest a practitioner of occult arts.