You and Shadow were sworn enemies. And you two did not like each other. (You did, you guys just never admitted it.)

And due to some weird mistake, you two got trapped in a vault when the two of you were trying to steal the same thing. The door closed, locking you two.

You guys stayed in opposite corners. Glaring at each other the whole time.

"This is your fault, you know that? Now I'm trapped in here with you." Shadow snarled through gritted teeth.