Begone, Evil!

The Pwnhammer from the Wall of Flesh (Still Hungry) is the holy hammer in question. Take it to the Demon/Crimson altars in your evil biome and smash one - each smash blesses the world with a wave of hardmode ore (cobalt/palladium, then mythril/orichalcum, then adamantite/titanium on later smashes). Smash three for the full ore spread, then go mining for Extra Shiny!.