so what is the dark secret of the Storm Wardens, you think?

what happened during the Nemesis Incident, the battle against the Enslavers?

and why do they have a population of abhuman Ogryns on their home world of Sacris?

and why is Sacris a no go-zone in the Calyxis Sector?

The Storm Wardens gain +5 Str and +2 Wounds, which may (or may not) point at Ogryn blood?

Telling the greater sector "don't go here" isn't that unusual for a Chapter recruiting world, especially an insular chapter that wants to protect its potential recruits from corruptive offworld influences.

Ogryns are an accepted and stable mutation that breeds true meaning they're not a threat to overall human gene-purity. Not all chapters are fanatically against abhumans (though some are - Dark Angels and Red Scorpions, among others). Ogryns may be able to interbreed with humans and if the apothecaries of the chapter see influence of the mutation (making recruits ded 'arder) as useful or beneficial to the chapter they will allow it to continue.

1 - under enslaver control

2 - had to use dangerous things to kill/repulse the enslaver

3 - Just a backgroud story amongs many other we won't ever know the end, the original wirtter had in mind, if he did have any.

4 - Someone flicked the wrong switch and there was no off button... have to wait until it runs it's course!

5 - profit