Tajuru Preserver

You may sacrifice a permanent to pay the activation cost of an ability, even if that ability comes from a permanent an opponent controls (such as Excavation).

If a spell or ability an opponent controls instructs you to perform an action unless you sacrifice a permanent (as Ogre Marauder does), you can’t choose to sacrifice a permanent. You must perform the action. On the other hand, if a spell or ability an opponent controls instructs you to sacrifice a permanent unless you perform an action (as Rishadan Brigand does), you can choose whether or not to perform the action. If you don’t perform the action, nothing happens, since you can’t sacrifice any permanents.

This ability affects only sacrifices. It won’t stop a creature from being put into the graveyard due to lethal damage or having 0 toughness, and it won’t stop a permanent from being put into the graveyard due to the “legend rule.” None of these are sacrifices; they’re the result of game rules.