Bloodstone

The Complete Kane Book 1 from Centipede Press

Kane, the mystic swordsman — an immortal, flame-haired sorcerer-warrior, cursed by an insane elder god to walk the Earth until eventually destroyed by the violence that he himself created.

In the dark swamp where toadmen croak and cower, slumbers an ancient relic of the days when creatures from the stars ruled the Earth. In the booty captured in a savage raid, Kane discovers a ring, a bloodstone, which is the key to the power that lies buried, inactive but not dead, within the forest.

Now Kane, whose bloody sword has slashed and killed for the glory of other rulers, can scheme to rule the Earth - himself!