Ryl'dhagt

Ryl'dhagt, also known as Ryl'dhagt of the Abyss, was an aboleth who partially led the takeover of Aquos at the Burning Knight's command. It was slain by the Champions Valoris.

Appearance
Ryl'dhagt was large creature with an eel-like body. It had a long tail fin that looks like a tentacle, along with four other actual tentacles, a spine running along its back, three eyes arranged vertically on its face, with a round mouth filled with sharp teeth below them, long whiskers and pasty flesh. Ashara has described it as looking like "an ugly thread" or "a tapeworm."

Personality
Ryl'dhagt was extremely manipulative, willing to use its ability to sense a creature's greatest desire to attempt to turn them to its side. It attempted to position itself as a friend to each of the Champions Valoris and made them impossible promises to attempt to sway them from the Aquosian cause. However, when its machinations failed, it was willing to dominate those it thought would be useful, as it did in the case of Dhudus. Further contrasting its helpful, welcoming façade, Ryl'dhagt possesses a tightly repressed rage, which it can unleash to psychically damage its enemies. When Briar first felt this anger, he observed that it felt as if that anger hadn't been fully unleashed in centuries. Ryl'dhagt also seemed very confident in its plans, sure that it had not failed even after its ally Kal'dazzum had been slain. On the other hand, it may have been bluffing in an attempt to demoralize the Champions Valoris, considering that it ultimately failed to accomplish any of its goals.

Background
According to legend, aboleths were created by Caugus when he stole the Lifegiver's clay of creation. In the war between good and evil gods, the aboleth served as one of the greatest lieutenants of the evil gods. It was set into the waters and had the power to speak into people’s minds and find their greatest desires to take advantage of them. If that failed, it could also enslave people through their minds, binding them to its will. Considering that the Champions Valoris were able to triumph over Ryl'dhagt, it feels unlikely that it was that specific aboleth, but it likely had similar origins or was descended from the original aboleth.

Ryl'dhagt entered an agreement with the Burning Knight, agreeing to find and turn over the Wreath of Persana in exchange for a kingdom, namely Aquos. It allied with a young kraken named Kal'dazzum, along with a horde of sea spawn and sahuagin. It also seems to have been given a number of the sea spawn forces, created by Kal'dazzum, to order around itself. When Princess Lotlyn was captured by sea spawn, Ryl'dhagt attempted to manipulate her, offering bring her brother Reides back to Aquos permanently. However, she resisted it. While Kal'dazzum remained fairly stationary in Coralpeak Citadel's throne room, Ryl'dhagt took up residence in the palace library. Presumably, it hoped to glean what knowledge it could from the library, but it left the books in a state of disarray. Ryl'dhagt was also much more active in surveying Aquos and its surroundings, frequently leaving the citadel to look for activity from the displaced Aquosians. On one such outing, it found a patrol led by Dhudus Laverath. It attempted to offer each patrol member something they would want, offering Dhudus well-matched, satisfying battles every day. When it was refused, Ryl'dhagt psychically enslaved the entire patrol. It puppeted Dhudus and used him to spy on happenings in the Aquosian camp.

Reides' Homecoming
During their mission to recover the contents of the lost armory in the Crystalline Trench, Ryl'dhagt left the palace to investigate, possibly having been alerted by the sahuagin the party encountered. As it searched the Trench, Jorah spotted Ryl'dhagt's tail, mistaking it for a kraken's tentacle. The party made plans for a hasty retreat, with Briar sealing the armory and the remains of those who had perished within behind them. However, the noise of the cave-in caused by Briar's Erupting Earth spell alerted Ryl'dhagt to the party's presence. It pursued the adventurers as they made their way to a shipwreck to hide the gear they had recovered. Ryl'dhagt quickly gained on the party, even with their magically enhanced swimming speeds, but stopped once it had almost caught them. Instead of attacking, it reached out telepathically to each party member and, as each mentally responded, sensed their greatest desires which it attempted to use to twist them each to its side. It offered Reides a place he would finally belong, saying that Khavas had betrayed him before and would disappoint him again. It attempted to convince Ashara that she had abandoned Kain forever and that the rest of the party would betray her, offering a share in the conquered Laverathia if she helped it. Apparently, it revealed a deep knowledge of Jorah's secret anxieties and told him it would help become a hero, his name written in the annals. It told Kilwin that it would help him balance his life, relieving him of the pressures of the light and allowing him to become his true self. It also offered its aid to Briar in his quest to find a new home for Terathun. After each party member refused it, Ryl'dhagt clarified that its offer was an open one and returned the palace.

The next day, Ryl'dhagt received intel on an impending two-pronged attack on Coralpeak Citadel from the possessed Dhudus. It learned that a large force would attack the front gates, while a smaller team would enter the throne room through a secret passage to attack Kal'dazzum directly. Ryl'dhagt informed its allies of these plans, allowing Kal'dazzum to prepare a number of sea spawn allies for the Champions Valoris' ambush. During the attack, Ryl'dhagt waited in the library with a number of sea spawn under its control. It also controlled a number of sea spawn opposing the frontal assault. As the battle progressed, Ryl'dhagt commanded Dhudus and his dominated patrol members to turn on the Aquosian forces, resulting in the deaths of almost the entire patrol group, except Dhudus, who was spared by Viglis. After Kal'dazzum's demise, the Champions Valoris swam to the library where they found Ryl'dhagt, who welcomed them inside. It revealed that Dhudus had betrayed Aquos, hiding that it was under coercion, and attempted to convince the party that it had actually succeeded in its plans. However, the adventurers were undeterred and engaged the aboleth in battle. While the encounter was harrowing, particularly for Jorah and Briar, Ryl'dhagt met its end when Jorah beheaded it with Quickbrand, which had been electrified by Reides's Lightning Bolt. Upon its demise, Ryl'dhagt's thralls seem to have been released from its controls. The remaining sea spawn in the main battle lost interest and abandoned the fight, while Dhudus seemed to have regained his senses when he awakened after the battle.

Goals
Ryl'dhagt co-led the 598 invasion of Aquos to obtain the Wreath of Persana for the Burning Knight, in exchange for dominion over the seas. It seems to have hoped to control the whole of Laverathia, with or without Kal'dazzum.

Abilities
Ryl'dhagt was a creature of legend and, accordingly, possesses legendary resistances that allow it to choose to succeed on a number of saving throws that it fails. It fought by lashing out at its foes with its tentacles and tail. Its appendages seemed to be covered in some harmful substance, although none of the Champions Valoris were affected by it during their battle. It also possessed a variety of psionic powers, such as telepathy, the ability to discern the greatest desire of those it spoke with telepathically, and the ability to charge the water around it with arcane energy powered by its rage, doing small amounts of psychic damage to its foes. Ryl'dhagt attempted to sway its enemies to serve its purposes, first by reading their minds and offering them what it thought they want to hear, then by psychically dominating them. According to Dhudus, this domination was experienced as being locked away and watching as your body is controlled by the aboleth. Ryl'dhagt was skilled at making those it puppets act as if they are acting of their free will, allowing its machinations and intelligence-gathering to avoid detection. The domination seems to have only been lifted by Ryl'dhagt's death. It could also summon an illusory wall that looked real and felt corporeal to those who were beguiled by it.

Ryl'dhagt and Kal'dazzum
Ryl'dhagt and Kal'dazzum entered an alliance to conquer Aquos, but the details of this alliance never became known to the Champions Valoris. Ryl'dhagt was described as leading the kraken into the city, but also as Kal'dazzum's general. While the specifics of their working relationship are unknown, Ryl'dhagt did not seem particularly upset to learn of Kal'dazzum's demise.

Quotes

 * (To Kilwin) "The pressures of the light cannot reach you here. [...] I wish to help you."
 * (To Reides) "I can give you the belonging you always wanted; the freedom you always sought. [...] You’re siding with the father who betrayed you."

Trivia

 * Ashara once mistakenly referred to the aboleth as an "abalor," apparently an old Elvish word for the creatures. It stuck.
 * Ironically, Ryl'dhagt managed to fulfill a few of the Champions Valoris' deepest desires with its death. Jorah was treated as a hero by the tritons who learned that he beheaded the aboleth, and the end of the invasion gave Reides the opportunity to begin repairing his relationship with Khavas, as well as the chance to become an ambassador for Laverathia.