You’re on the right track! This is an adjectival phrase— but what kind of adjectival phrase is this?

Marty’s presence at the dance was definitely a Catch-22 situation; if he talked to Cindy she’d be mad at him, but if he ignored her, there’d be hell to pay. His anger bubbled to the surface. He realized that by coming to the dance, he had brought his problems with him in a Trojan Horse, and he could only hope he would be able to keep them bottled up.