The Druid's Son (Fate of Shadows, Book 1) by Jamie Merril

Aleksey has always tried to be the hero, but after using blood magic to save Professor's life, he discovers he might not be after all.

Aleksey was only five when the King of Laeopeld locked him in a magic box. He wasn’t supposed to get out.
After two centuries in darkness, Professor wakes Aleksey into a world where sickness is spreading through the forest, and magic is fading fast. When they find a rare Roddŷr core, they think their luck is on the rise—until an ambush shatters their hopes, leaving Professor on the brink of death. With no other option, Aleksey uses forbidden blood magic to save him, trading one life for another.
After the spell ends, Aleksey miraculously survives, but something inside him has changed. Hoping to find a forest spirit who might hold the key to reversing the curse, Eira, an Elvish guard, takes Aleksey on a perilous journey. But with every step, his grip on himself weakens. Despite his best efforts, Aleksey is left to face an agonizing choice: save the forest and those he loves, or sacrifice everything for a chance at redemption.

"This was a lovely, emotional gem of a piece."
"Such a good read."
"This is a book that should be on everyone’s shelves."