Devoted Grafkeeper // Departed Soulkeeper — ruling 1

Disturb is found only on the front faces of some double-faced cards.

Devoted Grafkeeper // Departed Soulkeeper — ruling 2

If you copy a permanent spell cast this way (perhaps with a card like Double Major), the copy becomes a token that's a copy of the card's back face, even though it isn't itself a double-faced card.

Devoted Grafkeeper // Departed Soulkeeper — ruling 3

The back face of each card with disturb has an ability that instructs its controller to exile if it would be put into a graveyard from anywhere. This includes going to the graveyard from the stack, so if the spell is countered after you cast it using the disturb ability, it will be put into exile.

Devoted Grafkeeper // Departed Soulkeeper — ruling 4

"Disturb [cost]" means "You may cast this card transformed from your graveyard by paying [cost] rather than its mana cost."

Devoted Grafkeeper // Departed Soulkeeper — ruling 5

When you cast a spell using a card's disturb ability, the card is put onto the stack with its back face up. The resulting spell has all the characteristics of that face.

Devoted Grafkeeper // Departed Soulkeeper — ruling 6

A spell cast this way enters the battlefield with its back face up.

Devoted Grafkeeper // Departed Soulkeeper — ruling 7

To determine the total cost of a spell, start with the mana cost or alternative cost (such as a disturb cost) you're paying, add any cost increases, then apply any cost reductions. The mana value of a spell cast using disturb is determined by the mana cost on the front face of the card, no matter what the total cost to cast the spell was. (This is a special rule that applies only to nonmodal double faced-cards, including ones with disturb.)

Devoted Grafkeeper // Departed Soulkeeper : règles, fonctionnement et interactions (MTG)

Devoted Grafkeeper // Departed Soulkeeper is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

When this creature enters, mill two cards. Whenever you cast a spell from your graveyard, tap target creature you don't control. Disturb (You may cast this card from your graveyard transformed for its disturb cost.) Flying This creature can block only creatures with flying. If Departed Soulkeeper would be put into a graveyard from anywhere, exile it instead.

How it works : Devoted Grafkeeper // Departed Soulkeeper

Original English text — Wizards of the Coast / Scryfall

#1September 24, 2021· Wizards of the Coast
Disturb is found only on the front faces of some double-faced cards.
No other card is named in this ruling.
#2September 24, 2021· Wizards of the Coast
If you copy a permanent spell cast this way (perhaps with a card like Double Major), the copy becomes a token that's a copy of the card's back face, even though it isn't itself a double-faced card.
No other card is named in this ruling.
#3September 24, 2021· Wizards of the Coast
The back face of each card with disturb has an ability that instructs its controller to exile if it would be put into a graveyard from anywhere. This includes going to the graveyard from the stack, so if the spell is countered after you cast it using the disturb ability, it will be put into exile.
No other card is named in this ruling.
#4September 24, 2021· Wizards of the Coast
"Disturb [cost]" means "You may cast this card transformed from your graveyard by paying [cost] rather than its mana cost."
No other card is named in this ruling.
#5September 24, 2021· Wizards of the Coast
When you cast a spell using a card's disturb ability, the card is put onto the stack with its back face up. The resulting spell has all the characteristics of that face.
No other card is named in this ruling.
#6September 24, 2021· Wizards of the Coast
A spell cast this way enters the battlefield with its back face up.
No other card is named in this ruling.
#7September 24, 2021· Wizards of the Coast
To determine the total cost of a spell, start with the mana cost or alternative cost (such as a disturb cost) you're paying, add any cost increases, then apply any cost reductions. The mana value of a spell cast using disturb is determined by the mana cost on the front face of the card, no matter what the total cost to cast the spell was. (This is a special rule that applies only to nonmodal double faced-cards, including ones with disturb.)
No other card is named in this ruling.