Whenever a creature you control dies, you may pay . If you do, you gain X life.
"As she grew cold in my arms, I swore an oath that her funeral pyre would be dwarfed by a bonfire of our enemies."
Official Rulings for Vigil for the Lost
1/1/2011 : As the ability resolves, you choose a value for X and decide whether to pay . If you do decide to pay , it's too late for any player to respond since the ability is already in the midst of resolving.
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