PCs, take note: It’s always a bad thing when the ooze is more charismatic than you. Not to mention stronger, tougher, smarter, and wiser. In fact, unless you challenge an immortal ichor to a tightrope-walking challenge, stat for stat it will demolish the average PC. Hell, it can even fly!
What sets the immortal ichor apart from the many other mind-controlling atrocities that dwell in the Realms Below is that it is an object of power in itself. Like the One Ring or the Marvel Cinematic Universe’s Tesseract, it has wants of its own and can manipulate people/events to achieve them…but at the same time other Powers are going to want it. After all, if dragon scales make good magical armor and pixie dust can improve spellcasting, imagine what the blood of a god can do!
So the very sealed chambers and bespelled vessels that keep an immortal ichor from wreaking havoc on the world are also paradoxically what protect it. Once an immortal ichor gets loose, events are inexorably set into motion—either the ichor will attempt to claim its divine bloodright or it will be claimed in turn.
The Amaranthine Heart believes the world was destroyed. The little the immortal ichor “remembers” of its life as a god is the moment a mountainous chunk of moon slammed into it, while behind it the sky burned. In reality, the Amaranthine Heart is little more than a divine clot. (And the cataclysm it remembers is one the god it came from caused.) Blood from the crushed god’s body dripped into the deepest chasms of the earth, and there it has spent its time “saving the last remnants of existence” by creating a slave nation of troglodytes, mongrelmen, and strange aberrations. Upon encountering surface dwellers, the Heart will be stunned, exultant…and then furious at having been “forgotten,” “made a fool of,” and “left to reign over a kingdom of wretches.” Unless the surface-dwelling adventurers stop it, the immortal ichor will head straight to the surface to claim its rightful place as a god.
Known as the Sky Butchers and the Shrikes, the Lanian fleet rules the skies. The secret to their capital airships’ design is that each is powered by a trapped immortal ichor. When for the first time in history one of their carriers crashes, the immortal ichor gets loose and begins to set up a kingdom within the crashed hulk. The immortal ichor is also a clue to a mystery: The act of procuring divine blood for her mortal patrons—either her own or her rivals—is what has turned the formerly benevolent and wise Lanian patron goddess into a weak, vile, and impulsive shell of her former divine self.
A desperate immortal ichor recruits adventurers to protect it. Through its agents, it has discovered a humbaba is searching for it, planning to alchemically reduce it down to an ambrosia that will make the monstrous humanoid divine. The ooze is terrified it cannot fight off the stronger demonspawn and begs for protection. The party must weigh the risk of a Colossal monstrous humanoid scion of Pazuzu becoming a god versus allying themselves with an evil sludge that (for all its Wisdom) may not be able to resist its instinctual drive to dominate or devour its own allies.
—Pathfinder Bestiary 4 156
It’s unclear whether the immortal ichor needs to eat—after all, it’s immortal (duh) and it doesn't have the usual growing/dividing rules of more ravenous monsters. And anyway it’s more in the habit of dominating its victims rather than engulfing them. (Hell, that would just eat away their flesh, and nobody likes a juju skeleton when they can have a juju zombie.) That said…I like it when oozes eat people. And if you were a divine essence stripped of your immortal body and soul…wouldn’t you be down for a nosh on occasion?
If you’re looking for the immense tortoise, we covered that a few weeks ago.