Romulan 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.

How it works : Romulan

Original English text — Wizards of the Coast / Scryfall

No additional ruling has been published for this card.

Interactions with other cards

These cards' text mentions Romulan.

In the Pale Moonlight

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.) I — Each opponent sacrifices a nontoken creature of their choice. II — Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.") III — You may sacrifice an artifact or creature. If you do, create two 2/2 black Romulan creature tokens.

Sela, Tal Shiar Paradox

Whenever Sela attacks, exile up to one target card from a graveyard. Whenever one or more cards leave your graveyard, create a tapped 2/2 black Romulan creature token.

Cloak and Phaser

Strange new worlds — This spell costs {X} less to cast, where X is the number of differently named lands you control. Create two 2/2 black Romulan creature tokens. Draw two cards, then discard a card.