Mulldrifter
Creature — Elemental
Flying
When this creature enters, draw two cards.
Evoke 
If a strange, flying eel ever crosses your mind, follow it.
Jack Teagle
Secret Lair Drop (SLD)
• #1887Rulings
If you pay the evoke cost, you can have Mulldrifter's own triggered ability resolve before the evoke triggered ability. You can cast spells after that ability resolves but before you have to sacrifice Mulldrifter.
(wotc • 2021-03-19)
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as an evoke cost), add any cost increases, then apply any cost reductions. The mana value of the spell is determined by only its mana cost, no matter what the total cost to cast that spell was.
(wotc • 2021-03-19)
Rulings
If you pay the evoke cost, you can have Mulldrifter's own triggered ability resolve before the evoke triggered ability. You can cast spells after that ability resolves but before you have to sacrifice Mulldrifter.
(wotc • 2021-03-19)
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as an evoke cost), add any cost increases, then apply any cost reductions. The mana value of the spell is determined by only its mana cost, no matter what the total cost to cast that spell was.
(wotc • 2021-03-19)