Trechtus

In 1824 SMA, the vedalken twins Trechtus and Trathdan are born to their mother Hedda and father Khenoc in the sky city of Aether. Khenoc is a member of Aether's elected senate and Hedda is a wizard absorbed in her own research, so beyond their high-level schooling, the boys have a lot of time to themselves. Trathdan picks up a natural talent for artificiery and Trechtus takes after his mother, becoming a wizard and getting personal lessons from her when he can.
When the two are about thirty years old, Hedda mysteriously vanishes, sending Khenoc into a depressive spiral that isolates him from his children. Trechtus discovers Hedda's secret notes on a purely theoretical chronurgy magic, and Trathdan warns him to destroy them, worried that those notes are somehow responsible for their mother's disappearance. Trechtus ignores him and begins researching the magic, eventually becoming obsessed and making it his goal to discover what happened to Hedda. Trathdan finds out about this and threatens to tell their father. Trechtus illegally flees Aether that very night, traveling to the surface of the Silverlands and beginning his research on chronurgy.
In the Silverlands, Trechtus eventually settles in the outskirts of the small human town of Bridgeyard. The people there are wary at first, but after performing a few acts of service, they warm up to him as the local magic man. Trechtus researches what little he can of chronurgy for nearly a century, traveling to the great kingdoms of Arabas and Altis and even into the Underdark. He spoke with many creatures who could know about such magic, from Fey to undead. Despite all this effort, Trechtus gains nearly no leads. That is, until he learns of something called a "time crystal" locked away in a cave a few days from Bridgeyard.
Trechtus travels to this cave and notices odd time anomalies surrounding it. Undeterred, even encouraged by this odd magic, Trechtus delves into the cave and comes upon an old man named Jones, who warns him against taking the crystal. Trechtus ignores the old man's warning and kills his dog before swiping the crystal and taking it back home with him. He begins experimenting on it based off of instructions in his mother's notes, when one day an incident causes the crystal to explode, knocking Trechtus out. Upon awakening, he is alerted by the townspeople of an odd portal near the river, and when Trechtus goes to investigate, he recognizes the signature of chronurgy within it.
Bravely entering the portal, Trechtus is sucked into a time warp, witnessing visions of thousands of years of the past, including the birth and death of what could only be described as a primordial evil. Recognizing this evil to be on the Estrian Archipelago, Trechtus decides to travel there in hopes of learning more about it and about chronurgy.
The trip there is fraught with pirates, but Trechtus is sailing with a group of pirate hunters aboard the Catfish and even assists them with their business. During these battles, they rescue several ships the pirates had attacked, including two adventurers named Areth and Quaithe. Speaking to them and realizing that they are all headed to Estria to combat the same evil, they decide to form a three person party for the duration of their quest.
Upon landfall in Estria, Trechtus and the party meet a young girl named Teal who asks them to investigate a ruin in the jungle for her. The party senses that these ruins might give them a lead to their prey, and accept. Upon arrival at the ruins, Trechtus gives into his curiosity and uses his time crystal, causing it to be lost in the resulting rift before it closes, infuriating Trechtus.
The ruins are large, mysterious and full of ancient but functioning constructs. After unlocking the inner vault, they travel into it and destroy a particularly powerful construct called the Sentinel. What the Sentinel was guarding was exactly what the party was looking for: instructions on how to open a unique time and space rift. The notes detail that what was required is a spell to kickstart the rift (which Trechtus had already discovered), a strong energy source and a crystal to focus the energy. Satisfied, the group departs. Just outside the ruins the party encounters another group of adventurers and engage them in a fight, capturing a tabaxi druid. Quaithe convinces the party to release the druid against their better judgement. Afterwards, their first order of business is to get a crystal, which Teal informs them could be found in the Triton town of Novros. They travel there and acquire the crystal before fighting off an attack instigated by a Triton youth named Jerzeh, who was emboldened after being gifted a dagger by Trechtus. In the chaos, Trechtus loses sight of Areth and Quaithe and decides to return to the island to meet up with them. Waiting on the coast for Trechtus is a diseased looking wolf who speaks, inviting Trechtus to a meeting with "the King". Trechtus accepts despite his bad feeling and follows the wolf into a cave.
The King projects himself magically into the cave and offers Trechtus a deal. Work for him, and not only will the King return the time crystal that he had obtained from Trechtus, but he will assist him in finding the whereabouts of his mother, Hedda. Trechtus sees no better option than to accept, and the King sends Trechtus to Ordelia to kill the bugbear Sam Smorkle, who had outlived his usefulness. He meets back up with Areth and Quaithe, who had also decided to go after Smorkle, and together the three kill him and save Ordelia. With the party reunited, they travel to the south of the island where a large volcano called Mt. Folgath was located to find a good source of magic. A small kobold village at the foot of the mountain warns them to turn back, but they ignore the reptiles and push on, finding themselves in a dragon's den. Under the King's guidance, Trechtus kills one of the dragon wyrmlings and steals the Lord of the Mountain, a shard of the resident dragon's soul. They leave quickly and travel east, meeting back up with the Catfish and deciding that they should deal with the pirates, who had placed bounties on their heads.
The plan is simple and executed well: pose as captives to get the bounty and spring a trap. The fight is brutal, but they kill most of the pirates and their leader, the Admiral Idos Kyras. Satisfied with their work, they follow Quaithe's suggestion to find some local druids and make their way to Anaxi's Garden and meet Treefather Quinn. After participating in the druidic ritual in which Trechtus has a sour meeting with the King, Quinn informs them of an issue with a local Chimera in the Feywild, and they agreed to help him in exchange for his help with opening a time rift.
After traveling through the harrowing and corrupted Feywild, they kill the chimera. Trechtus decides to break his deal with the King and gives the King's power to the Fey Oeden, but is unable to hold the secret of his betrayal for any longer, and Areth forces him to admit that he had been working as an agent for the very evil they were chasing, though he had escaped from it. Areth is shocked and appalled by this revelation and Quaithe is disappointed but unsurprised. The two of them decide that Trechtus could redeem himself by helping them defeat the King, so they spare him. The party returns with a trophy, gaining Quinn's help. Fully prepared, the party heads back to the ruins to open up the rift.
Opening the rift is not difficult, and once inside the party heads to the lone castle within this pocket realm. There Trechtus finds a wisp that he is certain is what's left of the soul of Hedda, and gives it a protective home in the time crystal, which he had recovered. The adventurers encounter the source of the evil they were hunting: the King of Creation. With Thera's help and eventual sacrifice, the party defeats the King and seals him away for good this time. Despite more or less enjoying each other's company, the three decide to split up here.
Trechtus had been broken by the terrible things he had witnessed and been party to during his time on Estria. Realizing that the old man Jones was right in his warnings, Trechtus decides to return to the very cave he stole the time crystal from, vowing to protect it for as long as he lived.