Mox Sapphire 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

: Add .

How it works : Mox Sapphire

Original English text — Wizards of the Coast / Scryfall

No additional ruling has been published for this card.

Popular combos

Real combos played by the community, sorted by popularity.

#1
Cavalier of Dawn + Infinite Reflection + March of the Machines + Mox Sapphire
Infinite creature tokensInfinite death triggersInfinite creature ETBInfinite creature LTB
1Cast Mox Sapphire by paying .
2Mox Sapphire enters the battlefield as a copy of Cavalier of Dawn.
3Copy of Cavalier of Dawn enter-the-battlefield ability triggers, destroying itself and creating you a 3/3 Golem token.
4Copy of Cavalier of Dawn dies, triggering itself, returning Mox Sapphire from your graveyard to your hand.
5Repeat.

#1
Cavalier of Dawn + Infinite Reflection + March of the Machines + Mox Sapphire
Infinite creature tokensInfinite death triggersInfinite creature ETBInfinite creature LTB
1Cast Mox Sapphire by paying .
2Mox Sapphire enters the battlefield as a copy of Cavalier of Dawn.
3Copy of Cavalier of Dawn enter-the-battlefield ability triggers, destroying itself and creating you a 3/3 Golem token.
4Copy of Cavalier of Dawn dies, triggering itself, returning Mox Sapphire from your graveyard to your hand.
5Repeat.

Interactions with other cards

These cards' text mentions Mox Sapphire.

Sapphire Collector

Prowess When you cast your second noncreature spell in a turn, conjure a card named Mox Sapphire into your hand. This ability triggers only once. {2}{U}: Target instant or sorcery card in your graveyard gains flashback until end of turn. The flashback cost is equal to its mana cost.