Tangent 2 - what do Darkling and Dark Echo do?

[zgrssd]

In Tanget 2, there are one new building I can build 6 Dark Echo and there is 1 Darkling to capture.

But what do those buildings DO?
There is no tooltip, no video, not even a text message explaining them.

[illegal legos]

It's the Dark Beam and Dark Mirror from CW2. Darkling shoots out a beam that uses a ton of power but destroys creeper and emitters. Build Dark Echoes and target them directly with the beam to bounce it around terrain.