Necroth

Necroth seems to be a place filled with crypts that emit large columns of bones. The bones seem to react with purpose, forming a structure. In the non-canon Warcraft Adventures, Thrall obtains three scrolls from Drek'Thar, one of which is a spell that summons a bridge from Necroth. The spell requires a bone as a reagent in order for it to work.

Thrall says an incantation in order for the scroll to work which sounds like, "Dim balana gradazor. Nerada kurzol ne."

The visual effects of spell include a summoning of a large monster from Necroth, who subsequently turns into a walkable bridge. Thrall uses it to traverse to the other side of the chasm.

• Necroth is similar to the idea of Maldraxxus in the Shadowlands. They also have bone structures that grow.
• As evident with Thrall's multi-use of the Scroll of Shapeshift, it sounds like whoever used the scroll only needs to cast another incantation in order to use the spell again. Which means if Thrall has need of another bone bridge, he could create another. Though it's unknown if it would remove the first bridge or not.