Gatherer of Graces gets +1/+1 for each Aura attached to it.
Sacrifice an Aura: Regenerate Gatherer of Graces.
If Gatherer of Graces already has damage on it equal to its toughness minus 1, then sacrificing an Aura attached to it results in Gatherer of Graces being put into its owner’s graveyard before the ability that would regenerate it resolves.
The Aura you sacrifice doesn’t have to be attached to Gatherer of Graces.