locarno24 wrote:Because the rubric was supposed to 'cure the flesh change'.
It wasn't supposed to incinerate the physical forms of 90% of the legion. But it did.
It's not impossible that he knew that Ahrimans plan would/might do that and might never work entirely as planned.
In ahriman unchanged, he does try to rewrite the rubric armed with Magnus' own knowledge on the subject and.... well...Spoilers.
I read the whole trilogy.
I still am trying to figure out why Ahriman didn't go to Magnus for guidance on curing the flesh change, or if he did, why Magnus wouldn't help. Maybe he couldn't talk to Magnus. I think that must be it. No one was able to communicate with Magnus so they did it on their own, and THEN Magnus showed up like an

to punish them when they got it wrong.