Caverns of Despair — ruling 1

This has the supertype world. When a world permanent enters, any world permanents that were already on the battlefield are put into their owners' graveyards. This is a state-based action called the "world rule." The new world permanent stays on the battlefield. If two world permanents enter at the same time, they're both put into their owners' graveyards.

Caverns of Despair : règles, fonctionnement et interactions (MTG)

Caverns of Despair 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

No more than two creatures can attack each combat. No more than two creatures can block each combat.

How it works : Caverns of Despair

Original English text — Wizards of the Coast / Scryfall

#1October 1, 2008· Wizards of the Coast
This has the supertype world. When a world permanent enters, any world permanents that were already on the battlefield are put into their owners' graveyards. This is a state-based action called the "world rule." The new world permanent stays on the battlefield. If two world permanents enter at the same time, they're both put into their owners' graveyards.
No other card is named in this ruling.