Theres three methods, One is communion master/slaves. The second is doing the blood version of the same. The only other way is the crystal shield. There are crystals that allow your mages/priests to be a master or slave of a communion. This takes a combination of earth and astral to make. Look in your book to find the Crystal Matrix stones. That will give you the requirements to build these. Good luck on your future in dominions, its a really deep game. Bwaha.
PS. Hb is right about artifacts, I completely forgot them.
