Barrow/1.03.24

Undead
The Barrow is a rather small building that is needed to morph Skeletons into Wraiths (and, of course, Shadows). It offers 2 skills to research, which are specific to Wraiths and Shadows, and that's all there is to it. You'll only ever build one of these, probably purchase the 2 skills while it's being built and then forget about its very existence for the remainder of the battle.