Briarhorn
Creature — Elemental
Flash
When this creature enters, target creature gets +3/+3 until end of turn.
Evoke 
(You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)
Nils Hamm
Lorwyn (LRW)
• #199Rulings
If you cast this card for its evoke cost, you may put the sacrifice trigger and the regular enters-the-battlefield trigger on the stack in either order. The one put on the stack last will resolve first.
(wotc • 2013-04-15)
Rulings
If you cast this card for its evoke cost, you may put the sacrifice trigger and the regular enters-the-battlefield trigger on the stack in either order. The one put on the stack last will resolve first.
(wotc • 2013-04-15)