Collision of Realms — ruling 1

All creatures are shuffled into their owners' libraries at the same time. Then all players who shuffled nontoken creatures into their library this way reveal cards. Then all creature cards revealed this way enter the battlefield at the same time. Then all other cards are put on the bottom of their owners' libraries. Any abilities that triggered during this process are then put on the stack, starting by those controlled by the active player in an order of that player's choice, then continuing with each other player's abilities in turn order. The last player to put their abilities on the stack will be the first player to have their abilities resolve. A player who controls no creatures or who controls only creature tokens will still shuffle their library.

Collision of Realms — ruling 2

Each player reveals and puts onto the battlefield one creature card or fewer. They don't reveal a card for each nontoken creature they shuffle into their library; it's just one creature card at most.

Collision of Realms : règles, fonctionnement et interactions (MTG)

Collision of Realms 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

Each player shuffles all creatures they own into their library. Each player who shuffled a nontoken creature into their library this way reveals cards from the top of their library until they reveal a creature card, then puts that card onto the battlefield and the rest on the bottom of their library in a random order.

How it works : Collision of Realms

Original English text — Wizards of the Coast / Scryfall

#1February 18, 2022· Wizards of the Coast
All creatures are shuffled into their owners' libraries at the same time. Then all players who shuffled nontoken creatures into their library this way reveal cards. Then all creature cards revealed this way enter the battlefield at the same time. Then all other cards are put on the bottom of their owners' libraries. Any abilities that triggered during this process are then put on the stack, starting by those controlled by the active player in an order of that player's choice, then continuing with each other player's abilities in turn order. The last player to put their abilities on the stack will be the first player to have their abilities resolve. A player who controls no creatures or who controls only creature tokens will still shuffle their library.
No other card is named in this ruling.
#2February 18, 2022· Wizards of the Coast
Each player reveals and puts onto the battlefield one creature card or fewer. They don't reveal a card for each nontoken creature they shuffle into their library; it's just one creature card at most.
No other card is named in this ruling.