The forgotten gods

Thousands of millenia have passed while the gods of old have been forgotten, thus fallen in an everlasting slumber. A young male human named kaiya stumbled upon a stone plate, engraved with the names of these gods. Not knowing what they are he tried speaking them out loud, sounds, names that were supposed to be forgotten, never heard by living beings again, woke up the gods of old, who want revenge on the world for forgetting them. Meanwhile, kaiya gets a special class. An extremely strong 'unique' type class nobody has ever heard about, and some think it comes from worshipping the devils and sacrificing enough people. Kaiya needs to level his class, and quick. He can level up my getting experience points from killing creatures, the more dangerous the creature is to him, the more experience he gets for killing it.