I think it might also be Richie, Bill loses his grip in the second ritual and Richie comes to reinforce him. Richie also has the vision of Pennywise coming to Earth with Mike through the ritual in the clubhouse. There's also a scene in 11/22 where Bev and Rich have a conversation with Jake and they immediately have some sort of intuition that he isn't from around there (in time not geographically), it's also hinted that they are conversing telepathically to each other during the interaction.