Arkaine was a warrior who lived sometime before the events of the first Diablo game. He is noted for having been the first mortal to turn the tide of the Sin War in favour of the forces of Light, chasing the demonic legions back to the burning hells.
Arkaine possessed a magic armor called Valor, which, prior to his death, he hid within the Catacombs beneath Tristram. His hiding place consisted of a Hall of Fire (with Valor resting at the end of the hall) and a Gateway of Blood leading into the hall. Within the gateway was the Pedestal of Blood, and the gateway would remain locked until a person (the "Hero of Light") placed three Blood Stones atop the pedestal.
In the Diablo quest, Arkaine's Valor, the player must retrieve the three Blood Stones, one being located in the Gateway of Blood and the others in two side rooms, as well as overcome several Horned Demons, to acquire Arkaine's Valor, a unique Splint Mail.