Located at the sharp turn in Dead River Basin around ( 577, -21, 180 ) /waypoint 577, -21, 180. The entrance moves around this location, so has no exact location. Interact with a pile of dirt that highlights with the words a sink hole.
If you ever get lost, the exit is at: ( 957, -24, 1191 ) /waypoint 957, -24, 1191
Rumblers have always been a nuisance for Norrathians. These stone-snakes have recently burrowed into Dead River Basin and their tunnels bode ill for any unskilled adventurer.
The cave system is packed with numerous encounters of level 23-26 rumblers. Dispose of them at your leisure. There is no objective in this instance other than to cull their numbers. If luck is on you side, The Under Rumbler will be up at ( 848, -32, 1068 ) /waypoint 848, -32, 1068.