Magic Eater

Tad doesn't have any memory before waking up on the beach, apparently the sole survivor of a shipwreck. All he has from his past is a necklace with a symbol no one recognizes.

After growing up in the orphanage, he takes a job managing inventory for a merchant catering to adventurers. He knows he's a bit off, the world just smells different to him.

When he's confronted by a group of adventurers with more power than ethics, he learns that it's been magic he is smelling all along. As the confrontation builds he learns that he can eat that same magic, but it isn't enough to keep him from being taken.

Waking up in a dungeon, he quickly learns they are more than monster filled pits. They are tools of the Great System and just maybe doorways through the multiverse.

Now he must struggle to prove his worth, grow in power, and master his strange ability, all complicated by the fact that the enchantments on his gear might just be alive.