Solve for X, by R.C. McLachlan
Tony/Loki
Avengers movie!verse
17,421 words

Summary: “Suit yourself, Rudolph,” Stark says, tossing his empty soup bowl down and bringing up another false screen of light, tapping rapidly on it. “Find X.” Stark slides the image over to him, fingers pinning it down to the table, trapping naught but air and offering it as an olive branch. Whatever darkens Stark’s eyes when their gazes meet is not pity, not blame, and there are drops of onion soup in his ridiculous beard.

Loki slowly reaches over to tap the little X that is revealed once Stark lifts his thumb away and says, “I found it.”