Night Incarnate
Creature — Elemental
Deathtouch
When this creature leaves the battlefield, all creatures get -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.)
Anthony Palumbo
Commander 2018 (C18)
• #17Rulings
If a creature with evoke enters the battlefield without being cast, you won't have to sacrifice it.
(wotc • 2018-07-13)
Evoke is an alternative cost to cast the spell with evoke. It can't be combined with other alternative costs, such as casting a spell "without paying its mana cost."
(wotc • 2018-07-13)
The ability that causes you to sacrifice an evoked creature is a triggered ability. Players may respond to this triggered ability while the creature is still on the battlefield.
(wotc • 2018-07-13)
To determine the total cost of a spell, start with the mana cost or alternative cost (such as an evoke cost) you're paying, add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.
(wotc • 2018-07-13)
Rulings
If a creature with evoke enters the battlefield without being cast, you won't have to sacrifice it.
(wotc • 2018-07-13)
Evoke is an alternative cost to cast the spell with evoke. It can't be combined with other alternative costs, such as casting a spell "without paying its mana cost."
(wotc • 2018-07-13)
The ability that causes you to sacrifice an evoked creature is a triggered ability. Players may respond to this triggered ability while the creature is still on the battlefield.
(wotc • 2018-07-13)
To determine the total cost of a spell, start with the mana cost or alternative cost (such as an evoke cost) you're paying, add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.
(wotc • 2018-07-13)