Ruin Processor — ruling 1

If a spell or ability requires that you put more than one exiled card into the graveyard, you may choose cards owned by different opponents. Each card chosen will be put into its owner’s graveyard.

Ruin Processor — ruling 2

If a replacement effect will cause cards that would be put into a graveyard from anywhere to be exiled instead (such as the one created by Anafenza, the Foremost), you can still put an exiled card into its opponent’s graveyard. The card becomes a new object and remains in exile. In this situation, you can’t use a single exiled card if required to put more than one exiled card into the graveyard. Conversely, you could use the same card in this situation if two separate spells or abilities each required you to put a single exiled card into its owner’s graveyard.

Ruin Processor — ruling 3

You can’t look at face-down cards in exile unless an effect allows you to.

Ruin Processor — ruling 4

Face-down cards in exile are grouped using two criteria: what caused them to be exiled face down and when they were exiled face down. If you want to put a face-down card in exile into its owner’s graveyard, you must first choose one of these groups and then choose a card from within that group at random. For example, say an artifact causes your opponent to exile their hand of three cards face down. Then on a later turn, that artifact causes your opponent to exile another two cards face down. If you use Wasteland Strangler to put one of those cards into their graveyard, you would pick the first or second pile and put a card chosen at random from that pile into the graveyard.

Ruin Processor : règles, fonctionnement et interactions (MTG)

Ruin Processor 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 you cast this spell, you may put a card an opponent owns from exile into that player's graveyard. If you do, you gain 5 life.

How it works : Ruin Processor

Original English text — Wizards of the Coast / Scryfall

#1August 25, 2015· Wizards of the Coast
If a spell or ability requires that you put more than one exiled card into the graveyard, you may choose cards owned by different opponents. Each card chosen will be put into its owner’s graveyard.
No other card is named in this ruling.
#2August 25, 2015· Wizards of the Coast
If a replacement effect will cause cards that would be put into a graveyard from anywhere to be exiled instead (such as the one created by Anafenza, the Foremost), you can still put an exiled card into its opponent’s graveyard. The card becomes a new object and remains in exile. In this situation, you can’t use a single exiled card if required to put more than one exiled card into the graveyard. Conversely, you could use the same card in this situation if two separate spells or abilities each required you to put a single exiled card into its owner’s graveyard.
No other card is named in this ruling.
#3August 25, 2015· Wizards of the Coast
You can’t look at face-down cards in exile unless an effect allows you to.
No other card is named in this ruling.
#4August 25, 2015· Wizards of the Coast
Face-down cards in exile are grouped using two criteria: what caused them to be exiled face down and when they were exiled face down. If you want to put a face-down card in exile into its owner’s graveyard, you must first choose one of these groups and then choose a card from within that group at random. For example, say an artifact causes your opponent to exile their hand of three cards face down. Then on a later turn, that artifact causes your opponent to exile another two cards face down. If you use Wasteland Strangler to put one of those cards into their graveyard, you would pick the first or second pile and put a card chosen at random from that pile into the graveyard.
No other card is named in this ruling.