Capricious Hellraiser — ruling 1

The three cards you exile are chosen at random from among all cards in your graveyard. If all three cards you exile this way are creature and/or land cards, you won't be able to choose one of them to copy and cast. Capricious, indeed.

Capricious Hellraiser — ruling 2

You cast the copy while the ability is resolving and still on the stack. You can't wait to cast it later in the turn.

Capricious Hellraiser — ruling 3

If you cast a spell "without paying its mana cost," you can't pay any alternative costs. You can, however, pay additional costs, such as kicker costs. If the card has any mandatory additional costs, you must pay those.

Capricious Hellraiser — ruling 4

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

Capricious Hellraiser — ruling 5

If you don't want to cast the copy, you can choose not to; the copy ceases to exist the next time state-based actions are checked.

Capricious Hellraiser : règles, fonctionnement et interactions (MTG)

Capricious Hellraiser 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

This spell costs less to cast if you have nine or more cards in your graveyard. Flying When this creature enters, exile three cards at random from your graveyard. Choose a noncreature, nonland card from among them and copy it. You may cast the copy without paying its mana cost.

How it works : Capricious Hellraiser

Original English text — Wizards of the Coast / Scryfall

#1February 4, 2023· Wizards of the Coast
The three cards you exile are chosen at random from among all cards in your graveyard. If all three cards you exile this way are creature and/or land cards, you won't be able to choose one of them to copy and cast. Capricious, indeed.
No other card is named in this ruling.
#2February 4, 2023· Wizards of the Coast
You cast the copy while the ability is resolving and still on the stack. You can't wait to cast it later in the turn.
No other card is named in this ruling.
#3February 4, 2023· Wizards of the Coast
If you cast a spell "without paying its mana cost," you can't pay any alternative costs. You can, however, pay additional costs, such as kicker costs. If the card has any mandatory additional costs, you must pay those.
No other card is named in this ruling.
#4February 4, 2023· Wizards of the Coast
If the spell you cast 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.
#5February 4, 2023· Wizards of the Coast
If you don't want to cast the copy, you can choose not to; the copy ceases to exist the next time state-based actions are checked.
No other card is named in this ruling.