You create a gate into the Shadowfell.  You disappear from the Material Plane, and reappear at the beginning of your next turn.  You can reappear up to 1 mile away from where you entered.  Each time you use this spell, roll a d100.  On a roll of 91 or higher, you run into a dangerous denizen of the Shadowfell, and are disrupted.  Instead of teleporting, you take 4d6 necrotic damage and reappear in the same space at the beginning of your next turn.  If you roll a 42, you gain a mysterious benefit from an unknown force.  You regain 3d6 hit points, and gain a +1 bonus to damage rolls for 1 minute.

At Higher Levels.  If you cast this spell with a 5th-level spell slot or higher, you suffer no ill effects on a roll of 91 or higher, and gain the benefit on rolls of a 42, 7, 66, 96 and 13.