Something by Dakota Krout

Trapped between worlds. Potentia might be the way out. Time to kill Something.
Luke is an apprentice leather worker, training with his family to one day take over the business. He and his friends Andre, Taylor, and Zed have known each other forever, and swear that nothing will ever tear apart their friendship.
Then the Royal Decree comes. With the Dynasty of Dogs invading, and strange monsters appearing in the Hollow Kingdom, a draft has been implemented. Everyone seventeen or older is required to be tested for 'Potential'. If they have it, they will join the mysterious and renowned Ascender Corps. If not, they will be drafted into the Legion as a forced recruit.
Three of the friends test as powerful, or dangerous, classes of Ascender. Luke is found to have Potential, barely, but when he steps through the portal to begin his training. he is pulled to a plane that shouldn't exist. With no class trainer, the possibility of survival is low. Luke decides that he wants to live, and keeping his humanity isn't going to help.
His best chance is going Full Murderhobo.