Horrors are in the book! This is from an excellent source andlists out some new and some updated unit entries in the Wrath of Magnus!
via anonymous sources on Faeit 212
the book will have 9 new unit entries. some are new, some are updated with adjusted point cost and new options:
Scarab Occult Terminators
(yes you read that right, updated rules for Horrors aswell. the book in general will be a tzeentch like daemonkin, featuring all sorts of tzeentch daemons aswell)
there are 10 formations within the book and inside the detatchment.
there are 6 CSM formations and 4 Daemon Formations
There are Updates to Daemonic Loci as well as Icons of Chaos. The Aspiring Sorceror and Scarab Occult Sorceror have multiple wargear options.
the Tzeentch Discipline is added. there are also all 4 Traitor Marine Psychic Diciplines inside.
Magnus, Ahriman, Exhalted Sorcerors, Scarab Occult Socrerors aswell as Aspiring Sorcerors all have acces to 11 Disciplines (all 6 BRB Disciplines, all 4 Traitor Marine Disciplines aswell as the updated new Tzeentch one)
finally Ahriman is able to Cast powers of his Corvidae Cult ;) aswell as many, many more.