I don't like reducing monsters to statistics. But CR 24/MR 10 is a number that has its own gravity.
There are bigger, more powerful monsters in the Bestiary 4—demon lords and Great Old Ones and kaiju, oh my—but none of them have the dragon type. That still matters—even in these enlightened latter days, when we’re more about finding paths than we are about delving you-know-whats guarded by you-know-whos. At the end of the day, you picked up that sword to slay a dragon.
And this dragon was created by none other than a god. There are worse ways to start a tale…or end it, if PCs are unlucky.
So. The guardian dragon. As published dragons go, it’s second only to Mythic Adventures’s mythic wyrm red dragon in power (and that’s only by a hair). Its spell-like abilities are there to foil and confound you. Its immunities and resistances practically run the table. Its physical abilities and attacks—and there are so, so many of them—are designed to punish you this round and for several rounds in the future. It lairs in the farthest corners of the multiverse, can create demiplanes at will, and track all but Fine-sized intruders. It can grant its mythic power to allies or use it to literally remake the world around itself. And if you steal from it, it will find you—period.
A god of thieves has had his divinity stolen—a crime of such sublime irony that the god would laugh in delight, were he not terrified for his new life. (Gods of thievery have a talent for making enemies with long memories.) Worse yet, when he returned to his divine realm to retrieve an old blade still invested with his power, his guardian dragon servitor refused—or was unable—to recognize him as its master. Believing retrieving the sword is the first in a series of necessary steps to reclaim his mantle, he teams up with some of his greatest mortal worshippers (or perhaps just some mortals unfortunate enough to be in his debt) for the (second-)greatest heist of all time: to steal from himself.
It’s the perfect heist. Ally with your enemies to break into a guardian dragon’s secret lair and steal its divine treasure. Wait for—and ideally survive—your enemies’ sudden but inevitable betrayal. While they flee with the artifact, guardian dragon in hot pursuit, you return to the lair to clean out the dragon’s personal treasure after its private demiplane collapses. Abscond with the treasure, race to your enemies’ location to finish off any combatants left standing, and claim the divine artifact as your own as well. Again, it's the perfect heist. What could possibly go wrong?
On some worlds, color is not the only allegiance. On Helia, the elemental tide that pulses with every dragon’s heartbeat is stronger than any skin tone or moral/ethical pole. As Fire dragons war with Earth and Water, only the beasts of Air and Cold stand apart, maintaining the balance. But when a pair of guardian dragon siblings (which in itself should be an impossibility) joins the war on the side of the Water Sept, it may forever shift the balance of the war—and the makeup of Helia itself. An adventuring company’s sovereign dragon patron begs them to come out of retirement for one last mission: end the threat of the guardian dragon twins or die trying.
—Pathfinder Bestiary 4 146–147
I love me some one-off dragons. Where my gorynyches at?
With that centurion-like armor and spiraling snake tail, Jorge Fares’s design for the guardian dragon underlines its singular nature. Interestingly, while it has only two non-winged limbs, it appears to have true arms like a lamia noble rather than the crude forearms of a linnorm or the legs of the more birdlike wyvern.
Also, how much do you want to bet that planting the teeth of a guardian dragon would sprout udaeoi?
Finally, while guardian dragons don’t have a vomit attack per se, their blood is poisonous dragon bile and their breath is a lingering poisonous cloud… Does that make us three for three on puke-themed monsters this week?