Currently being developed by modder Cruze Bear, it’s still a work in progress. Footage of the mod was uploaded by Cruze Bear to his YouTube account, showing two Ori’s navigating the Sunken Glades. Thankfully they’re two different colours, so no confusion there.
In it’s current state, you can teleport to eachother if you fall behind and if the host Ori dies, then both players are sent back to a checkpoint. If the joining Ori dies, they can actually be revived, though Cruze Bear states this might not actually be a factor when the mod is completed
While apparently still “far from release”, it’s a promising look at a new way to play through Ori And The Blind Forest. Whether this is a mechanic we’ll be seeing in the sequel is another matter. If not, maybe Cruze Bear will mod it in too.