With the vision, it wasn't a question anymore that the House of Horin was trying to get rid of Varion. If his father hadn't found him on time, someone would probably found Varion in a crazed state, or died from 'mental disturbance'. People would think it was stress from losing the reclamation project and moving on.
From the words he spewed unconsciously during that state, there was also a possibility that the clan wanted him to attack Trinity openly using Celestia's espers to create chaos, and they would take advantage of said chaos to try and capture Zein again.
Whatever it was, it would be a bad end for Varion either way.
In the end, Darleon agreed to their deal after Radia modified it greatly. The old man would create a faction inside Celestia as intended, as well as look for any evidence they could use against the House of Horin. Meanwhile, Varion would stay hidden.