This whole thing would look like the makings of a Harry-Molly coup against Mab if we didn't know better.
Molly is acquiring external power for Harry (usurping/allying Kringle in Harry's name, letting mortals know HE helped them...), and Harry is always rebelling against Mab, and clearly rubbing that off on Molly. Granted they're also aligning against Marcone by affecting humans in Chicago, but well, he's a Denarian now and all.
And yeah, the reindeer are probably a mask of Sleipnir. Who knows, maybe Rudolph just IS Slepnir, same as Kringle is Odin.