On Supernatural Season 13 Episode 20, Gabriel is trying to get revenge on the guys who sold him over to Asmodeus. Unfortunately he gets into a fight with one of the demigods, and since his grace isn't completely healed, he gets wounded. Gabriel is able to track down the guys, who are looking for him, and he's able to get their help. 

Dean asks him what he is after, and Gabriel admits he his trying to go after Loki's sons because it's their fault he was sold to Asmodeus. Dean is reluctant to help him out because he knows how going after revenge ends, but Sam is able to convince him to help out. The guys are able to track down Loki to a local hotel penthouse, but are quickly greeted by his two sons. Sam, and Gabriel fight them off, and Dean goes off to search for Loki.

Dean gets to Loki's penthouse, but he quickly learns Loki has just left of a projection of himself. The guys head back downstairs to help out Gabriel who has the real Loki cornered. Gabriel is able to get the upper hand, and he quickly kills Loki. 

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