Professor Onai’s Assignment is a quest available in Hogwarts Legacy.
Your objective is to collect Troll Bogeys and cast Depulso on a levitated enemy. Eventually, you’ll learn Descendo.
Here’s a walkthrough & guide of Professor Onai’s Assignment in Hogwarts Legacy.
Cast Depulso on a levitated enemy
All you need to do is to find an enemy in the woods and use Levioso on it.
Then, cast Depulso while it’s levitated and the objective is cleared.
Find Troll Bogeys
Next, you have to acquire 1 Troll Bogeys. You can buy it from J. Pippin’s Potions in Hogsmeade.
Another way is to fight a Troll at the Troll Lair.
Beat the Troll and you can loot Troll Bogeys.
Talk to Professor Onai
Next, you have to attend Divination Class during the day.
Talk to Professor Onai after the lesson is over.
You will then learn the spell Descendo. The quest ends here.