Zalavexus

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.

This monster can see in all directions simultaneously and therefore can't be flanked.

A monster with this ability regains the given number of Hit Points each round at the beginning of its turn.

This monster doesn't have a single mind (typically because it's a swarm of smaller creatures), and is immune to mental effects that target only a specific number of creatures. It is still subject to mental effects that affect all creatures in an area.

When the worm that walks is reduced to 0 HP, it discorporates and the component worms that make up its body disperse in every direction. If even a single worm escapes, the worm that walks will eventually re-form using a process that typically takes 1d10 days. While the exact circumstances and surroundings determine how long the worm that walks's foes have to dispatch the fleeing worms before they escape, usually its foes have only a single round. Typically, this requires the application of an area effect or splash weapon within 1 round to the space where the worm that walks collapsed. After any amount of area or splash damage is dealt to that space, the character dealing the damage must attempt a DC 15 flat check. Each subsequent area or splash damage effect performed on the area reduces the DC of this flat check by 2, to a minimum of DC 5. If any of these flat checks succeed, none of the worms escape, and the worm that walks is destroyed permanently. At the GM's discretion, clever means of trapping or otherwise detaining the vermin may extend the time allowed to finish off the worm that walks.

Frequency once per day Effect If Zalavexus's next action is to cast a 3rd-or lower-rank spell or cantrip, reduce the number of actions to cast it by 1 (minimum 1 action).

The worm that walks Strides, ending its movement sharing a space with a creature, and deals 4d8 piercing damage to the creature. The creature can attempt a DC 27 reflex save.

If a reaction would disrupt Zalavexus's spellcasting action, he attempts a DC 15 flat. On a success, the action isn't disrupted.

The worm that walks collapses into a shapeless swarm of worms. It drops all held, worn, and carried items. While discorporated, the worm that walks can't use attack actions and can't cast spells, but it can move through areas small enough for its individual worms to fit without having to Squeeze. It can use the same action to coalesce back into its normal form.