That's an end crystal Crafted from a ghast tear, 7 glass and one eye of ender. You can only place them on top of obsidian or bedrock, but if you remove the block they're on they don't break, so you can make nice decorations with them.
Apart from the above: you normally use these for either decoration or to (re)summon the Ender dragon. And well... you can either craft them or look around to buy 'm in shops I guess. I'll see if I got some spares lying around, mind want to keep taps on your inbox (see /mail command).
Great minds think alike indeed.... PS: I took the liberty of blaming you for this idea, always easier to blame someone else for your own diabolical schemes