This is buged ???

I got this axe from DoA
and try to put a 15^50 mod on it but is not possible... why ?

I would guess the reason is because it is not inscribable. All the weapons that are say "inscription: none" and that one is decidedly lacking.

That axe doesn't have an inscription slot. Not all weapons in Nightfall spawn with an inscription slot. :\

ok guy's thankz for the input...