Investigate the Circus Tent - Baldur's Gate 2 Side Quest
The Circus Tent dungeon is found in the center of Waukeen's Promenade, there will be a guard blocking the entrance at first. When you approach the guard will warn you that foul magic is afoot and you'll be able to persuade him to move and let you inside.
Upon entering the Circus Tent you'll meet a Genie who will stop you on your way across the bridge and ask you to answer a riddle. Answering correctly will get you 19,500 EXP. If you answer wrong he'll give you a second riddle which will reward you with 14,500 EXP if you get it right. Answering both riddles wrong will result in him attacking you, defeating him gets you the least amount of EXP of all.
Below you can find the answers to both riddles that he asks.
Riddle #1 Answer: The prince is 30 and the princess is 40
Riddle #2 Answer: Nothing
In the next room you come across you'll meet an Ogre with a girl's voice that goes by the name Aerie. She will ask you to collect a sword from the Peasants just north of her that will free her from her chains and illusion. You'll have to force attack the Peasants since they'll be neutral to you when approaching them. Freeing her will net you 18,500 EXP so I recommend you do it, it'll also make Aerie available as a companion immediately instead of having to wait until we complete this dungeon.
When you're ready to continue with this dungeon head into the room north of Aerie. You'll be ambushed by Werewolf and Shadow enemies when you enter, so long as you have +1 weapons you will be able to hit them and they should be no problem for you. Proceed up the stairs in this room and you'll find the final room of this dungeon where Kalah resides.
Kalah is a pretty easy fight, he'll mostly attack Quayle who is currently an ooze giving you plenty of time to take out the Shadow and Werewolf enemies then focus on him. Defeating Kalah will result in the illusion inside the Cirus Tent to be dispelled and everyone to return to normal. Once this happens you'll get some dialogue with Kalah after which you'll be rewarded 25,000 EXP.
Before leaving the tent make sure you loot what Kalah dropped, Ring of Human Influence, Elves Bane and a scroll of Stoneskin. Talk to Hannah inside the tent for another 500 EXP and the Amnian Soldier outside the tent for +1 Reputation. With that we're officially done with the Circus Tent dungeon!