Published Adventures – How Can Investigators Ban Abhoth Permanently?

If you want to follow the rule book, they could create a door right under Abhoth, leading this abomination to another time / world / dimension

Door spells

The idea of ​​a sign that would open on a distant world
Eibon was impressed as being rather fantastic, not to say far-fetched.
– Clark Ashton Smith, The door of Saturn
.

Cost: Variable POW, see Table XIII: Travel and Door Creation Costs
access a door: variable magic points and 1 health point
Incantation time: one hour per POW spent. Gate spells allow the caster to
create doors between other lands or eras, dimensions or
worlds – allowing the user to travel great distances with
simple step. Usually, a door connects to only one other location.
The creation of a door requires the constant expense of prisoner of war, in a sacrifice equal to the log at the base of the distance traveled.
The door connects in five times miles. A door can take many forms,
the most common being indicated by a pattern of lines painted on
a particular soil or arrangement of stones in a field. Using the
Gate costs a magic number of points equal to one fifth of the prisoner of war
originally used to make the door. Each trip through a door costs 1
No health. If the user lacks enough magic points for a trip,
the traveler spends health points to offset the costs. Return trips
by a door always costs the same price as the original trip.
Usually, no matter what or anything can move through a door, although some have been built in such a way that a certain key, word or
gesture – is required to activate the portal. Some versions of
We know that the spell "changes" also those who pass, to help
survival on a foreign world. There are also hints that some doors are
capable of more than one destination.

But you can create the spell you want, you know. The rulebook invites you to do it! :

Chance variations

There is no definitive fate. the
those listed here are just a guide and a starting point for the
Guardian to use.

(…)

Change a spell

Try to insert personal keys into the
spell, linking it more closely to your scenario,
investigators and history, if possible. Place: consider the
places in your story; any of them could it be related to
the spell? If the investigators are dealing with ghouls, for example
For example, a spell that must be thrown underground suddenly takes
on an added dimension. Spelling components: the specific elements
necessary to cast the spell. Could it be that the investigators
need the curved silver dagger that they saw during the previous session at the
English Museum? Spell Ritual: Usually a larger spell effect
means a more complex and involved ritual. Consider where,
when and how the spell is cast. Do the investigators
smear themselves in the blood at the full moon and write
a ritual circle? Description of the spell: it can go from subtle to
dramatic. Try to imbue the description with strange smells,
disorienting visions, curious sounds and disturbing sensations
I think most of these spells undermine the pitcher's sanity,
and the way you describe the cast should make it
manifesto