Lukas Trevelyan (1) was well versed in all of the magic taught by the circle, but after receiving the mark, it started becoming evident that his powers are starting to take a new shape. It wasn't until he was trapped alone in a cave after the assault on Haven when his new powers started surfacing, as he opened a fade rift that sucked the demons who attempted to attack him.
After settling in Skyhold, Lukas sent for someone who can understand these new powers. Through training with Your Trainer and consulting with Solas, he started developing rift magic, gaining almost full control over them, and prevented the loss of his old powers.
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Lukas Trevelyan (2) studied math and engineering while staying at his family's castles. His acquaintances would try to invite him to parties and outings, but he'd refuse, stay at home and try to craft something functional. He had always wanted to create a crossbow of his own, and learning how to use it, however it was no easy task. Days after days of trying and failing started frustrating him, but didn't stop him. During one of his family's parties his former engineering teacher noticed Lukas in his room tinkering with a barely functional crossbow. He conversed with Lukas, and Lukas opened up to him about his frustrations. The man offered Lukas to teach him how to fire a bow, and promised that once he got the hang of it, he'll begin to understand how a crossbow works as well, and it'll help him master his creation.
Months of training left Lukas as an extremely skilled marksman, and with all the fun he had with the bow, he forgot about his crossbow work.
It wasn't until moving to Skyhold till Lukas regained his interest in engineering and crafting. A letter from Leliana recommending specialization trainers had the name of the famed Three-eyes, a master artificer. Immediately he called for him, and trained in ways of an artificer. His background and knowledge made him a fast learner, and he learned numerous crafts that could help him in battle, and while he still hasn't crafted his crossbow yet, he still intends to do it.. someday.