Once per day, a glissan can cast a sleep spell. The spell affects a single creature, without restriction, including those of more than 4+4 HD, any undead, and certain other creatures specifically excluded from the effects of a normal sleep spell (see the spell description and the Monster Manual). Any target is allowed a saving throw; those who are normally subject to sleep spells save at -2.
Agreed to making it unique and single-target.
Like a telperan, a glissan can polymorph itself into the shape of a human or demi-human child about seven years old. The glissan can also assume the shape of a songbird, a seagull, or a miniature unicorn (2’ high at the shoulder). As a unicorn it becomes AC 4, runs at 24", and strikes with horn and hooves for 1-4/1/1.