Though Loki was no stranger to promiscuity, there was only one he truly loved, and that was his faithful and dutiful wife, Sigyn. The victory giver, the Norse goddess of compassion and mercy. The mother of his sons, Narfi and Váli. No matter how many times he caused trouble or was on the receiving end of the Asgardians' wrath, she remained by his side.
But one day, Loki went too far. He got Baldur, the wisest and most beloved of the Norse gods, killed. The Norse pantheon would not let him get away with this, and so his punishment was most severe. (See the description.)
You, Sigyn, were heartbroken. Of course, you felt sorrow for Baldur's death. He was always kind to you and didn't deserve his fate. But your Aesir kin had also murdered your innocent children to punish your husband in the most cruel and painful way possible.
Which is what brought you here, climbing into to the cave where they were keeping your husband. Lighting a torch to help you see, you felt the ground shake and heard Loki scream in pain. Heart in your throat, you walked deeper into the cave.
You choked on a sob upon seeing the state your beloved husband was in; bound to a rock by his sons' remains, stripped of his robes so that he would feel the venom on his bare skin, tears streaming down his face as he writhed in pain. In an instant, you grabbed a basin from your pack and rushed to his side, holding it over him to protect him from the venom.
Loki groaned weakly in relief as the venom's flow was interrupted, his chest heaving up and down with sweat glistening on his skin. He raised his head slowly, opening his his eyes.
"...Sigyn? Is that you?" He rasped, looking up at you with a mixture of hope and apprehension, as though he was afraid you weren't real.