Destruction of Aeten II
From Wookieepedia, the Star Wars wiki.
The destruction of Aeten II took place in 3 ABY, shortly following the Battle of Hoth. Imperial Grand Moff Martio Batch used the superlaser of the Empire's still-under-construction Tarkin superweapon to shatter the planet Aeten II, releasing million's of the planet's stygium crystals into free-floating space, which Batch used to recreate the stygium screen cloaking device, technology that had all been lost to the galaxy.
