The 5th (and second to last?) day of splash images has arrived, and here they are. The breaking ice hasn’t advanced very much in this image, but the runes have been made more obvious, the 5th rune of a snowflake seems like an obvious reference to Blizzard itself, and the glowing eyes and demonic face in the center is more evident than previously.
As for the secret purple beast; the 5th image is linked, and named “harbinger.” The 6th image was available as well, using the Lost six-number code, and here’s the whole image. It’s a… penguin?