PC Query mystery block?

[LordKronsell]

I've seen a block, 2x3, red with purple orbs, like a chest but unopenable, unable to open, mine, use an axe, hammer, dynamite (blow up) and seems unaffected by anything I do. Any ideas? This is why i came to the forums, it's bugging me and I haven't a clue

 

[DemonSword]

It is a Crimson Altar, same thing as a Demon Altar on a Corruption world (Purple Spiky Thing). Uses are the same for both. Making Boss Summon items and Night's Edge.
You need a item called Pwn Hammer to break it after defeating a certain boss. (final boss of Prehardmode)