No mictlan/lanka, eh? Then take your pick of Niefel, Ashdod, Tir Na N'og or Gath. If Niefel or TNN, take an E9/N4+ bless. If one of the others, take E10/n4+. Or if you want to try something other than an E/x bless, try say, ma Ermor. Shadow Vestals bless nicely with something like w9/s9. Or Kailasa, s9/a9/N-or-E4 (/gets blasted for this last one
), or... yeah, any of these should work.
Btw, sacred serpents are a terrible sacred. They are just way too hard to keep alive. Taking a strong bless for those is a waste of points. They are better for keeping your morale up than anything else. If you want a bless as c'tis, consider primarily what you might like on your sacred summons.