At first it seems there's no end to him, that his life and his power just go on forever and anything that wants to consume them completely will be occupied for the rest of time.
And then—there is an end—but not the end; as the last drop of power breaks free, the whole thing comes roaring back to life, restored in an instant, good as new—
—and then he explodes?
It's not really an explosion per se; it's a chaotic storm of power, centered on the spot just in front of her all-devouring maw where his body was just beginning to reappear when instead it started doing this. Blazing light and utter darkness, searing heat and bitter cold, lash out in whirling arcs from that central point; and other things too, less nameable things. A wave of force that flings her into the air like a doll and carves deep furrows in the sand of the seabed, shattering the parts that have fused into glass. An energy that turns scattered fragments of seaweed into enormous plants sprouting amid the wreckage, no two alike; a second, opposing energy that crumbles all living things it touches into dust. All the parts of this storm move independently, spinning around and over and through each other, so that over the course of a second a single scrap of seaweed is burned, frozen, given new life as a ten-foot-tall flowering tree with a crown of peacock feathers, then violently torn apart by opposing arcs of force and each of the dozen pieces crushed, warped, half-destroyed at random by the invisible energy of decay, and burned and frozen all over again, all the while being alternately illuminated by near-blinding beams of light and veiled in impenetrable darkness.
Somewhere in the middle of all that, there might or might not be a wavering silhouette that might or might not be the Emperor. It is nearly impossible to detect him by any means, and entirely impossible to reach him; and the storm is growing, reaching outward to encompass the debris it scatters across the sand.