: You are probably right though how would he know when
: neither he nor Balor had access to the Total Codex?
Actually, it's entirely possible that Soulblighter knew about the Summoner from the Total Codex, because, as you'll remember from "Flight from Covenant," you see SB in the northern half of the map, who turns to crows when you get near him. If he was hanging around that close to Covenant at the time, it's probable that he could have read the entire Codex and just left it there for the Legion to find, for some purpose of his own.
Doom 0^)