Center of All
Center of All is generated randomly as part of normal monster generation, rather than in a guaranteed lair. However, entering the golem level (Sum of All) in the Neutral Quest branch greatly increases the odds of Center of All appearing, so he will most likely appear while the player is in that branch. Center of All is permanently invisible and can easily surprise players who do not have the ability to see invisible.
Besides dealing physical damage in melee, Center of All is able to throw cursed loadstones at his opponents. These thrown loadstones deal 1d30 damage and have a 1/3 chance of adding themselves to the target's inventory instead of dropping to the floor. In this way, Center of All can quickly weigh down and immobilize his opponents.Like an iron golem, Center of All is slowed by lightning and healed by fire attacks.
Compass all the planes,
and yet you will never find
[ riff on a Planescape Haiku, originally by Ecco-Mono ]