I
CREATURE 7Genderless alien entity of unknown provenance
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 monster with telepathy can communicate mentally with any creatures within the listed radius, as long as they share a language. This doesn't give any special access to their thoughts, and communicates no more information than normal speech would.
1d8+8 bludgeoning, DC 22 basic Fortitude
Note: A DC was not provided for this ability by Paizo. The DC present here is a moderate DC for the creature level according to the Gamemastery Guide creature building Tables.
The monster deals the listed amount of damage to any number of creatures Grabbed or Restrained by it. Each of those creatures can attempt a basic Fortitude save with the listed DC.
I makes up to four Strikes with different arms, each against a different target. Each attack counts separately for their multiple attack penalty, but the penalty doesn't increase until all attacks have been made. If I subsequently uses the Grab action, they can Grab any number of creatures they hit with Writhing Arms.
The monster can instead use Grab and choose one creature it's grabbing or restraining with an appendage that has Grab to automatically extend that condition to the end of the monster's next turn.