It seems this new version is set in the world of Mennara? Has this world ever been used before? Any other info on it?

I think it's all terrinoth (different continent maybe)

A runewars developer update thingy was named "building combat worthy of mennara" and in the descent 2nd edition information it referenes both mennara and terrinoth later down the page.

Mennara is the name of the world. Terrinoth is the main setting for most of the games in that world, (Runebound, Descent, Runewars, Rune Age, Dungeonquest).

Other lands in the world of Mennara include:

Torue Albes, (Runebound: The Island of Dread, Descent: Sea of Blood).

Al-Kalim, (Runebound: Sands of Al-Kalim).

Isheim, (Runebound: The Frozen Wastes).

Zanaga, (Runebound: Mists of Zanaga).

Ah, thanks for clearing that up.