Ninkilim
Spoiler warning: Articles include story details through Episode 47 of the main campaign and all three episodes of Parental Advisory.
Ninkilim is the name attached to Todd's petrified rat and later used for the large rat-headed patron. Their exact relationship is not fully resolved.
Todd discovers the petrified rat during an archaeological excavation. It sometimes animates or speaks, urging him toward the power beneath Aelmor. Other private mental voices are explicitly distinguished from its earlier voice.
At the chapel a dark presence leaves the rat, enters Guthber and escapes. Todd later speaks of having been deceived for fifty years, while earlier language mentions forty; the duration is inconsistent.
Shala calls the being who restores Todd during the festival their new patron. Rory uses Ninkilim for that large being while connecting the earlier petrified rat's occupant with the Dragon King. A shared name is not sufficient to merge the two presences.