If you believe it was a vision from a deity; Epona, Rhiannon, Apollo, Odin, and/or Morrigan all seem like very plausible gods/goddesses to be symbolized in your vision. Since it was a vision that was frightening, I would definitely look into The Morrigan. She is one scary goddess to work with, but what I hear it is incredibly rewarding.
Before assuming it was a vision from the divine, I personally would also look into the symbolic meanings of a horse and a crow. Perhaps even meditate upon what they vision would mean to you if it was your own subconscious telling you something. Scrying is my favorite way to work out visions!