You were absentmindedly pulling mobs in The Thundering Steppes and somehow you've stumbled into a large gnoll-infested tunnel system. Next time, think before you act!
What happened is that you wandered too close to a Splitpaw GnollTerraporter, and were attacked by the guards - specifically a Tesch Mal abductor, who upon touching you teleported you to this instance. Your goal here is to escape captivity and find a way back to the surface. What you are looking for is a functioning terraporter, which can be found at: ( -52, -65, -234 ) Copy/waypoint -52, -65, -234. Use the various movable object and your battle skills to maneuver your way to that location.
If for some reason you desire to enter gnollish captivity, then you must be hit by a Tesch Mal abductor. One abductor patrols around each of the terraporters. If they are gray to you, then you can attack/aggro them or another gnoll that is linked with them to force an abduction. They only have to hit you once to send you into the instance. All terraporters are found along Thundermist Road in The Thundering Steppes: