Most of them are Gods, but they should still be possible to be weakened, wounded, and slain. Now that order is dead, the fate of peace is in the hands of our few retainers, the only beings capable of slaying these Gods. He commanded this army to destroy anyone and everyone who defied them, Gods, Beasts, or Terrarians alike, until once again, precious few remained. This lasted until an arrogant child and his pet dragon sought to put an end to this madness, and repeat history, conquering the Gods one by one, until he had created himself an army. Since then, Gods and Terrarians coexisted in harmony, and reconstructed civilization. One Terrarian in particular, convinced the Gods to turn against Cthulhu, ultimately resulting in the supreme God's downfall, creating the Crimson in the process. Vast populations of Terrarians were slain for their amusement, until only precious few remained. The reluctantly obeyed, plunging the world into chaos. After these Gods existed for millenia, one in particular, Cthulhu, crowned himself the King of Terraria, and forced all other deities to serve him.
As Terrarians, the dominant, humanlike species of Terraria, have begun to construct civilization, certain Gods were created by various means to govern such a world, and strip the Terrarians of their free will. The Terraria Multiverse hosts a variety of creatures sentient or otherwise, that make up this otherworldly dimension.