Slithering Rift

Tremorsense allows a monster to feel the vibrations through a solid surface caused by movement. It is an imprecise sense with a limited range (listed in the ability). Tremorsense functions only if the monster is on the same surface as the subject, and only if the subject is moving along (or burrowing through) the surface.

A slithering rift is so clear that it's difficult to spot. A successful DC 48 perception check is required to notice a stationary slithering rift, and a creature must be Searching to attempt this check. A creature that walks into the rift's space might fall into any pit currently in effect due to Dimensional Pit.

Ingesting an extradimensional space like that found in a bag of holding deals 12d8 force damage to the slithering rift and its occupants. The slithering rift then immediately uses Out You Go.

The slithering rift opens an extradimensional, 20-foot-deep pit that covers its own space and all adjacent squares unless they are walls or similarly blocking terrain. Any other creature occupying spaces in the pit must succeed at a DC 40 reflex save or fall into the pit, taking damage from the fall (typically 10 bludgeoning damage). Any creature grabbed by the ooze is released from the Grab and falls in, even if it was outside the pit squares. While the pit is open, the slithering rift is Immobilized and can't be forced to move. It can make pseudopod Strikes originating from the walls of the pit. A creature that starts its turn at the bottom of the pit takes 5d6 acid damage. Creatures can climb the walls with a DC 40 athletics check. When the slithering rift dies, the pit closes and creatures inside are ejected, as Out you Go.

The slithering rift makes a single pseudopod Strike against each target within range it hasn't already Grabbed. These attacks count toward the slithering rift's multiple attack penalty, but this penalty doesn't increase until after all of these attacks.

The slithering rift closes all pit spaces it created using Dimensional Pit, ejecting all its occupants onto the ground into random free spaces where the opening of the pit was. Each occupant takes 9d6 bludgeoning damage (DC 40 reflex save).

Trigger The monster's last action was a successful Strike that lists Improved Grab in its damage entry, or the monster has a creature Grabbed or Restrained Effect If used after a Strike, the monster attempts to Grapple the creature using the body part it attacked with as a free action. This attempt neither applies nor counts toward the creature's multiple attack penalty. The monster can instead use Improved Grab as an action and choose one creature it's grabbing or restraining with an appendage that has Improved Grab to automatically extend that condition to the end of the monster's next turn.