Iacobus ("yuh-KOE-biss"), Chief Dolphin of the Aegean and the Ionian, swam swiftly away from CoralKeep. With Poseidon and Amphitrite lying ill of a disease that Asclepius himself could not cure, Iacobus had suddenly become the default Ruler of the Seas. He really shouldn't have left CoralKeep so abruptly, but, after all, he was off to find the cure. Although both sea-monarchs were immortal, the disease nevertheless left them sapped of strength and Power/Magic. The sea itself was beginning to show signs of chronic withdrawal of the sea-gods' life-giving Magic; the tide stayed unusually low, fishermen waited in their boats to no avail, and high, booming waves had capitulated to soft undulations of water.
With a mind impossibly racing faster than he was swimming, Iacobus went over for the hundredth time the words of the Oracle at Delphi. Apollo had been kind enough to bring the head priestess from the temple to the coastline and the waiting dolphin.
Heed the Pythoness. The cure will not come from the gods, for an immortal's touch renders the healing plant useless. Nor can a human obtain the plant, which is anchored to the water's floor. Only a sea creature nourished at infancy with mother's milk can bring back the cure. Under waters cursed by the death of a cloud's daughter, in the light of the shadows, shall be the cure.
The first part of the message was easy enough to understand. Only a dolphin, a sea mammal, would be able to find the mystical plant. Yet in order to figure out who the "cloud's daughter" was, Iacobus had to travel back to CoralKeep and pore over all the historical/mystical Encyclopedic Tomes stored in the royal library. After a week of deciphering crabbed handwriting and odd symbols (whoever did the recording was fond of using his own shorthand), Iacobus had heard a chance remark made by three chattering dolphins that cloud goddess Nephele had returned to Olympus to wail yet again over her ill-fated life. Remembering that Helle, Nephele's daughter by King Athamas of Boeotia, had drowned in her future namesake, the Hellespont, Iacobus had rushed like a madman out of Coralkeep, leaving the three gossips staring after him. Fortunately Iacobus already had an empty pack strapped to his tail (he had meant to gather medicinal herbs that day) or he would have had to go back for one to lug back the mystical plants in; a dolphin, who was armless in any case, obviously could not have carried back a load of healing plants.
And so, a scant hour away from CoralKeep, advancing to the Hellespont, Iacobus tried to solve the Oracle's last enigma.
Besides being incontestably oxymoronic, the phrase "in the light of the shadows" could mean a variety of things. The Pythoness could have been referring to the fact that light is dimmed underwater, that luminescent fish resided in the dark depths of the Hellespont, or that the healing plant itself shone underwater. Yet all of these notions seemed to be excessively ridiculous/stupid interpretations for a rather solemn riddle.
Pushing such discouraging thoughts out of his head, Iacobus headed on resolutely.

After the passage of just three days, Iacobus arrived at the mouth of the Hellespont. As he stared at the awesome, blue corridor he would have to explore, he once again regretted his impulsive departure: having neglected to bring a traveling companion, Iacobus had had a hard time trying to catch food and getting rest when he was required to be on the lookout for hostile animals. But because he had found what he believed to be the answer to the last riddle, he put aside his weariness to deal with later.
Tunneling through the Hellespont's shoreline cliffs were vast cave systems whose apertures became visible only at exceptionally low tides; even then, only a few inches of the shadowed roofs were visible. Obviously, boats and swimmers were unable to navigate the immersed tunnels and reach the interior. Yet Zeus, wanting a hideaway, had ordered Hephaestus to line the interior of one system with smooth/reflective silver and gold, so that a single, weak ray of light entering the interior from the watery tunnel could illuminate all the inner chambers. Perhaps, at the floor of the tunnel leading to Zeus' hideaway, in the light of the shadows, grew some of the curative plants.
Yet after having searched all the cave systems of the entire northern shore of the Hellespont in a scant day (ah, the wonders of adrenaline), Iacobus had found nothing but rocks in the few caves where the tunnels had led anywhere; there were no plants in the oppressive darkness of the passageways. Already he had turned himself around to begin searching the southern shore in a homeward direction. But what if he found nothing? Iacobus tried not to dwell on that probability.
At the third opening he encountered, Iacobus noticed rays of light exuding from it, causing the hole to be brighter than the submerged cliff face.
Suppressing a dolphin cry of joy, Iacobus swam up the tunnel, heedless of anything growing on the tunnel's floor, of the fact that the glowing tunnel dwarfed him. First and foremost he wished to see if the chamber really was coated in precious metals.
When the tunnel's roof yielded to air, Iacobus surfaced and surveyed the cavern.
The cavern was dome-shaped, reminiscent of an overturned silver bowl. The rounded ceiling was lavishly studded with sapphires imitating the zodiac's constellations; a gold sun gleamed from the dome's apex. Passageways, bright from the reflections of the light from the tunnel, led to glowing sleeping chambers. Furniture carved from huge pearls and opals crowded the solid half of the dome bottom, also silver; the Hellespont's waters occupied the half where Iacobus floated, gaping in the delphinic manner.
Enough sense returned to Iacobus to make him look back at the forgotten tunnel floor. Malachite palm trees about ten centimeters high, growing through cracks in the silver coating of the floor, waved their fronds at him. He quickly/gently uprooted a few dozen with his mouth and deftly maneuvered them into his pack.
In a few seconds, even the ripples caused by Iacobus' passing had disappeared from the cavern.