Weapon die increase question

[Hubbaman]

Hello!

I'm looking into effects that increase the damage die of weapons.
I know that lead blade (an internal size increase) stack with actual size increase, like from enlarge person, and that internal increases don't stack with each other.

What I wonder about is how the second obedience from the Empyreal lord Falayna works.

Strong Arm (Su): As a swift action, you can increase the damage die of your weapon by one step for a number of rounds per day equal to your HD. These rounds need not be consecutive.

It don't give the weapon an size increase, it only changes the die.
1) Would this stack with lead blades?
2) Would it give an increase based on the weapon die (2 steps for 1d8 for medium weapon, 1 step if less) or would it be 1 step only?

If it don't stack, it's a really bad second obedience, compared to what you would get from the other Empyreal lords.

Thanks in advance!
Hubba

[Chemlak]

It’s a virtual size increase. No it wouldn’t stack with LB, and it would be a number of steps as normal for the size increase FAQ.

[Hubbaman]

Thanks for the answer!

I had a sliver of hope for it to stack, as the ability does not say anything about size (as lead blades and impact), but that's okay.

Cheers
Hubba