The Crimson altar is the counter part to the Demon Altar it works the same as the Demon Altar so it can also be used to craft Slime Crown, Bloody spine, Worm food and the Suspicious Looking Eye.
When Hardmode is active you can use a Pwnhammer to brake the Crimson altar when broken it spawns 1 of the 6 Hardmode ores into your world Titanium Ore, Cobalt Ore, Mythril Ore, Adamantite Ore, Palladium Ore and the Orichalcum Ore