There are no hints on who this mystery person is but there are several names that are available. Those names include Toni Storm, Athena (Ember Moon), Nixon Newell (Tegan Nox), among others.
Here is everything announced for next week's Dynamite and Rampage:
FTR vs. Gunn Club
Darby Allin vs. Andrade El Idolo
The Bunny vs. ??? (Owen Hart Cup Qualifier)
House of Black vs. Evil Uno, Stu Grayson and Fuego Del Sol
More matches will be announced in the coming days on AEW's social media accounts.