17 cards where the set is “otj” and the card types include “mount”

Archmage's Newt (Outlaws of Thunder Junction #39)
Bounding Felidar (Outlaws of Thunder Junction #5)
Bridled Bighorn (Outlaws of Thunder Junction #7)
Calamity, Galloping Inferno (Outlaws of Thunder Junction #116)
Caustic Bronco (Outlaws of Thunder Junction #82)
Congregation Gryff (Outlaws of Thunder Junction #200)
Drover Grizzly (Outlaws of Thunder Junction #161)
Fortune, Loyal Steed (Outlaws of Thunder Junction #12)
Giant Beaver (Outlaws of Thunder Junction #165)
Gila Courser (Outlaws of Thunder Junction #124)
Ornery Tumblewagg (Outlaws of Thunder Junction #171)
Quilled Charger (Outlaws of Thunder Junction #139)
Rambling Possum (Outlaws of Thunder Junction #176)
Seraphic Steed (Outlaws of Thunder Junction #232)
Stubborn Burrowfiend (Outlaws of Thunder Junction #184)
The Gitrog, Ravenous Ride (Outlaws of Thunder Junction #206)
Trained Arynx (Outlaws of Thunder Junction #36)

The message was clear to Sorin—time to search for something else.