The weapon in question was the Department of Mysteries' "weapon", which is a giant, spinning ball of pure, raw magical energy. It's not a traditional weapon like a sword or gun, but rather a force of nature harnessed by magic.
It's important to note that:
* The weapon itself wasn't controlled by anyone. It was simply unleashed and caused havoc in the Department of Mysteries.
* The Ministry of Magic blamed Voldemort's forces for it, but ultimately, it was Dolores Umbridge's actions that triggered the weapon's release.
Let me know if you have any other questions!