Ashiok, Nightmare Muse — ruling 1

Any effect that exiles a card exiles it face up unless that effect specifies otherwise.

Ashiok, Nightmare Muse — ruling 2

The card exiled while resolving Ashiok's second ability may be the one that was returned to its owner's hand.

Ashiok, Nightmare Muse — ruling 3

If Ashiok's second ability returns a token to its owner's hand, that player can't exile that token from their hand. They must exile a card from their hand if possible.

Ashiok, Nightmare Muse — ruling 4

You may cast any face-up cards your opponents own from exile while resolving Ashiok's last ability, not just those exiled by Ashiok's second ability or by Ashiok's Nightmare tokens.

Ashiok, Nightmare Muse — ruling 5

If you wish to cast any exiled cards, you do so as part of the resolution of Ashiok's last ability. You can't wait to cast them later. Timing permissions based on a card's type are ignored.

Ashiok, Nightmare Muse — ruling 6

If you cast a spell "without paying its mana cost," you can't choose to cast it for any alternative costs. You can, however, pay additional costs, such as kicker costs. If the card has any mandatory additional costs, such as that of Thrill of Possibility, those must be paid to cast the card.

Ashiok, Nightmare Muse — ruling 7

If a spell has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.

Ashiok, Nightmare Muse — ruling 8

In a multiplayer game, if a player leaves the game, all cards that player owns leave as well. If you leave the game, any spells and/or permanents you control from Ashiok's last ability are exiled.

Ashiok, Nightmare Muse : règles, fonctionnement et interactions (MTG)

Ashiok, Nightmare Muse 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

+1: Create a 2/3 blue and black Nightmare creature token with "Whenever this token attacks or blocks, each opponent exiles the top two cards of their library." −3: Return target nonland permanent to its owner's hand, then that player exiles a card from their hand. −7: You may cast up to three spells from among face-up cards your opponents own from exile without paying their mana costs.

How it works : Ashiok, Nightmare Muse

Original English text — Wizards of the Coast / Scryfall

#1January 24, 2020· Wizards of the Coast
Any effect that exiles a card exiles it face up unless that effect specifies otherwise.
No other card is named in this ruling.
#2January 24, 2020· Wizards of the Coast
The card exiled while resolving Ashiok's second ability may be the one that was returned to its owner's hand.
No other card is named in this ruling.
#3January 24, 2020· Wizards of the Coast
If Ashiok's second ability returns a token to its owner's hand, that player can't exile that token from their hand. They must exile a card from their hand if possible.
No other card is named in this ruling.
#4January 24, 2020· Wizards of the Coast
You may cast any face-up cards your opponents own from exile while resolving Ashiok's last ability, not just those exiled by Ashiok's second ability or by Ashiok's Nightmare tokens.
Card named in this ruling
Nightmare
#5January 24, 2020· Wizards of the Coast
If you wish to cast any exiled cards, you do so as part of the resolution of Ashiok's last ability. You can't wait to cast them later. Timing permissions based on a card's type are ignored.
No other card is named in this ruling.
#6January 24, 2020· Wizards of the Coast
If you cast a spell "without paying its mana cost," you can't choose to cast it for any alternative costs. You can, however, pay additional costs, such as kicker costs. If the card has any mandatory additional costs, such as that of Thrill of Possibility, those must be paid to cast the card.
No other card is named in this ruling.
#7January 24, 2020· Wizards of the Coast
If a spell has in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.
No other card is named in this ruling.
#8January 24, 2020· Wizards of the Coast
In a multiplayer game, if a player leaves the game, all cards that player owns leave as well. If you leave the game, any spells and/or permanents you control from Ashiok's last ability are exiled.
No other card is named in this ruling.