The Blue Scribes
The Blue Scrubz, otherwise known as Xirat'p and P'tarix (yep, their names are just reversed) are a pair of Blue Horrors in the service of Tzeentch.
Tzeentch has tasked them with discovering every last spell and piece of forbidden knowledge there is to know, in an attempt to boost his own power and rise to the top of the Great Game. However, wary of what might happen if someone else got their hands on this information, or the pair began letting all this knowledge get to their head, he put a safeguard in place. P'tarix is able to use runes and glyphs to record spells, but can't read so has no idea what he's writing. Xirat'p can read the spells his brother writes, but has no idea what spell it actually is. Presumably this leads to Three Stooges-esque arguments at every opportunity.
On the Tabletop
Filling the category of Tzeentch's unique Herald alongside the Changeling, the Blue Scribes are a HQ unit for Chaos Daemons. On each turn during the psychic phase, pick a psychic table and roll a d6, auto-manifesting that power with no warp charges expended.