Were you looking for the Web of Ungoliant?
The Mystery web is a semi-rare drop of the Mirkwood Spider that is said to be the remains of its last meal.
Once thrown by right-clicking, it will drop various items (some useful, some not so much) including, but not limited to: leather armour, bones, swords, rings, gold nuggets, silver nuggets, very rarely mithril nuggets, iron, rotten flesh, compasses, weapons and daggers, or even a slice of melon (this is one of two ways to obtain melons in Middle Earth, the other being a semi-rare spawn in Far Harad, this method probably being easier).
However, the player should never think that a mystery web marks the end of their fight, because the Mystery Web can also spawn small Mirkwood Spiders (any type of them can spawn).
Although this item is technically a "weapon", owing to the fact that it can be thrown, it deals neither damage nor knockback to its target.