Sigil of Power with Blood Magic

Small mechanics question here.
As far as I could gather so far, the unique staff "The Burden of Shadows" still comes with the usual sigil of power implicit.
Which is an ability that gives increasing damage multiplier buffs the more mana you spend.
But the staff converts the mana cost to a life cost.
So is the ability pointless? Or is it actually skill cost based on your mana, without needing to pay mana?
Seems unlikely, but it likewise seems odd if this unique was put on just the staff where it can't use the implicit.

No real intention to bump, but I edited the OP to make it more abstract - could be quite interesting to know whether abilities that scale of a % of character resources spent work if the cost is converted to something else.
I will test this as soon as I can, which sadly might be a while.

It's probably answered in an oversight, like all those cultist bows with % increased phys damage on them.

In every previous iteration of a buff based on mana cost, mitigating the mana cost by converting to x cost means it doesn't count toward the proliferation of the buff.

I don't know the answer in this specific case, but it's a relatively safe guess to assume if you aren't paying mana, you aren't benefiting from a buff that works based on mana paid.

Edit: On looking at the staff, I'm guessing it's just an oversight or a previous iteration holdover that it has sigil of power, because sigil of power definitely shouldn't work when you're paying life for abilities.