How works the power of astropath ? ( additional d10 on perils of the warp table , he swap the additional die for the tenth or unity of his d100 ? )

( i m french sorry for my awful english )

I do not have my copy with me to verify, but if my memory is right than Phenomena/Perils occur if you roll doubles on the percentile roll to manifest.

-=Brother Praetus=-

Yes basically he can swap either die rolled on the perils. Don't forget the talent an astropath gets also allows him to replace any roll lower than 75% with his/her signature effect. (I forget the name of the talent.) Overall it's fairly hard to produce a really bad result with an astropath even when pushing.

The talent you're thinking of is Rite of Sanctioning