Ayara cherished her new machine servitors just as much as she once did her many suitors: not at all.

Ayara, Widow of the Realm // Ayara, Furnace Queen

At the beginning of combat on your turn, return up to one target artifact or creature card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step.

{T}, Sacrifice another creature or artifact: Ayara, Widow of the Realm deals X damage to target opponent or battle and you gain X life, where X is the sacrificed permanent's mana value.
{5}{R/P}: Transform Ayara. Activate only as a sorcery. ({R/P} can be paid with either {R} or 2 life.)

March of the Machine

{T}, Sacrifice another creature or artifact: Ayara, Widow of the Realm deals X damage to target opponent or battle and you gain X life, where X is the sacrificed permanent's mana value.
{5}{PR}: Transform Ayara. Activate only as a sorcery. ({PR} can be paid with either {R} or 2 life.)

March of the Machine Promos

The first activated ability of Ayara, Widow of the Realm uses the mana value of the permanent you sacrificed as it last existed on the battlefield, not its mana value in the graveyard.