Calculated Dimension for HierarchyBelongsTo

[HonestToad]

I have used the HierarchyBelongsTo function to create a table that lists each node, together with all the possible ancestors

I would like to create a calculated dimension that returns the parent node fields for the selected nodes parents (Ancestor.Level=-1). 

I have managed to solve this problem in a number of ways...

=aggr(nodistinct only(if(Ancestor.Type='$(=Only({<"=Num([Ancestor.Level])"={'-1'}>} Ancestor.Type))',Ancestor)),Node)

However, I am struggling using the Only function when there are multiple parents - I would like to return all possible parents if that is possible.  

Does anyone have any ideas?