Make your way to the mission marker, grab the poster, and head inside. . . where Sabal and Amita will send you to kill Noore.
Back at Shanath, you can’t use the main door to the arena. So look right, directly above the newspaper hanging on the column, to find a grapple point. It and another swing-grapple sequence will put you in front of the air vent. And just like that, you’re in.
Inside, sneak through the back halls—don’t worry, there’s no one here to see you—until you reach the control room. Take out the two guards here, then press the buttons to release all the animals at once (tiger, bear, rhino, and wolf). They’ll wipe out Noore’s gladiators (though you can help if you like).
An enraged Noore, thinking you’re just an incompetent employee, will send guards to kill you. Destroy them (there’s no need for stealth here) as you make your way to Noore. You might want to free the tigers in the holding area just for fun—though you’d better believe they’ll come after you if there are no enemy soldiers around.
When you get to Noore, you could shoot her, but we suggest you wait instead. The “confront” option will play out, and you’ll get a memorable cutscene that completes the mission.