Feeding The Beast
From UO Excelsior Wiki - Ultima Online Free Shard
To summon Chief Paroxysmus you must obtain 8 items. 7 items from Putrid Slimes and 1 from the Putrifier.
Getting Started
To start off you will want to kill Putrid Slimes all around the dungeon, and the 3 Putrifiers and collect the summoning items listed below.
Putrid Slime Items
 Blackened Heart
|
 Rotting Head
|
 Severed Left Arm
|
 Dismembered Torso
|
 Severed Right Arm
|
 Severed Left Leg
|
 Severed Right Leg
|
Putrifier Item
 Rabid Brain
|
Summoning Chief Paroxysmus
Once you have all the summoning items you are ready to engage battle with Chief Paroxysmus.
Work your way to the end of the dungeon and choose which Paroxysmus you would like to battle.
For the Extreme Paroxysmus (Currently Not Available) use the west box, for the normal Paroxysmus use the east box.
The summoning altar looks like this:
