OK so everyone make sure you go back and read Will's last post. He changed it quite a bit.
So with that being revised some of the events are awkward.
So, the alter is in that main part of the main map. A once-great-hall with half the walls and ceilings blown off.
How about, we say that, Herbert went over and examined the alter, then walked back away from the alter in order to meet Ryann.
While they are talking with Ryann over by the edge near the bridge, that is when Will and Dzel move in from the stairs. A mixture of poor weather, bad voodo, and being grossed out by the carnage keep the parties from noticing one another. We can say it far enough away for this to be realistic as this castle is very large.
So, Herbert, Dimitri, and Ryann will have to head back toward the alter to get to this hallway they saw earlier that they are talking about.
So Team Will-Dzel and team Herbert-Dimitri-Ryann will meet in the alter and not the below room.
Does this make sense?