Board Thread:Warhammer 40k General Discussion/@comment-91.224.27.226-20131031140001/@comment-3258762-20140108170941

Slug gunner fan wrote: I don't understand this debate about height but Im ust personally say that Magnus was IMO and TMK the tallest Primarch. I always personally imagined him as being about 20 feet tall while the other Primarchs were around 12 feet or so. He was the tallest, but it's mostly a psychic facade during his battle with Leman Russ. After recieving extreme punishments, it dropped, showing him as about the same height as Russ.

I do, however, believe that Russ also shrunk, indicating he too had a psychic facade, which might indicate that all Primarchs had it and it was an unconcious thing.

To note: They're still described as larger than Astartes, so they're still fairly huge, but it could be that the Primarchs seemed larger because of this psychic field around them, which probably helped amplify their presence.