Blood Aspirant

Blood Aspirant can be sacrificed to pay for the cost of its own last ability.

If you sacrifice a permanent as part of casting a spell or activating an ability, Blood Aspirant's first ability will resolve before that spell or ability.

Blood Aspirant's first ability is a triggered ability, not an activated ability. It doesn't allow you to sacrifice a permanent whenever you want; rather, you need some other way of sacrificing permanents, such as its second ability.