I love the juggernaut for three reasons:
1) It’s a “basic” D&D survivor, originally from X10 Red Arrow, Black Shield and the Creature Catalogue, that has managed to roll all the way from the Known World to Golarion. (MYSTARA 4 LYFE, yo.)
2) I love monsters that are customizable based on domains. Dunno why, I just do. (Actually, I do know why—I like that it lets you surprise your players and worldbuild on the cheap to boot. And if you want to randomly determine what a juggernaut’s keyed domains are, not to mention create deities on the fly, you can use the chart I created way back in the “Graven Guardian” entry.)
3) A shrine that is also “alive” that is also a steamroller? That earns kill points!?! How could I not love that?
But even though the juggernaut is a vicious-trampling, spell-hurling faith tank, it still offers fun tactical and role-playing options for the party. The faith-bound trait, for instance, means that a smart low-level party that manages to steal a couple of vestments can walk right by the same juggernaut that a dumb, more powerful party has to go toe-to-toe with. And since a juggernaut counts as a shrine, capturing or destroying one might earn the party a morale advantage in combat, relief from enemy spell effects, benefits like Influence and Magic during campaign downtime, or the eternal enmity of a god, all depending on your group’s play style.
Also it’s a giant steamroller of (un)holy death. That part’s still pretty cool.
A juggernaut’s Destructive Aura (Su) was its own undoing, after an enemy priest sacrificed an artifact to rob the juggernaut of its fast healing and cripple its wheels. A spark of life still burns somewhere within the animate altar, however. Adventurers who brave the storms that tend to surround the juggernaut (courtesy of Weathermaker (Sp)) have a chance to repair and reconsecrate the construct…but they may accidentally end up restarting its rampage.
With their massive wheels, great bulk, and the elaborate priesthoods that support them, most juggernauts are anathemas to nature worshippers, symbols of the indefatigable onslaught of civilization. The massive druidic engine Thornstrike is thus a bizarre oddity, an Unstoppable (Su) stone table-topped altar that trails wall of thorns in its wake.
Skerrin, the Seven-Walled, is circled by a juggernaut dedicated to the Lawgiver once per day. A magical bell atop the juggernaut is chimed on the hour, blessing Skerrin’s curtain wall with the magicks that have made it thus far impregnable. To breach the wall and open the Skerrin’s doors to an army, adventurers will first have to cripple the juggernaut. That means not only fighting the Lawgiver’s priesthood and otherworldly servitors, but also the axiomite and inevitable auditors who do not wish to see such an immaculate construction come to harm.
—Pathfinder Bestiary 4 162–163