Tolhoth was originally a tribal god, but became a god of war as his tribe conquered its neighbors and founded a nation. Quite apart from the struggles of his worshippers, he waged war in the realm of the jealous gods, a dimension of unending strife between many gods.
As his earthly following grew, his own victories diminished in glory and reward, eventually leading to a string of stalemates and eventually defeats. He descended to the earth and consulted the Great Oracle of Pellan, whose vision extended throughout all dimensions. She told him that as he was victorious on earth, he would suffer defeat in the sky.
Tolhoth appeared as a fiery giant towering over the tops of mountains, destroying every person and every temple in every city of village where he was venerated. Nothing remained of the nation that had worshipped him, and the neighbors swarmed in to take possession of anything of value that remained.
Speaking his name became taboo, lest it be mistaken for a prayer and invite his wrath.
On occasion someone is born with a connection to Tolhoth. Although they don’t know the name of the great being they are connected to, they can feel his might and they are, for all intents, clerics. They might found their own cult or they might keep what they know to themselves.
In either case, they draw power away from Tolhoth, who no longer bothers to look upon the earth. He is too drawn into his cosmic wars to feel even the slightest sensation. Should he somehow learn of these clerics, he would undoubtedly find some way to destroy them, either in person or by proxy.