Asari Captain — ruling 1

A creature attacks alone if it's the only creature declared as an attacker during the declare attackers step. For example, Asari Captain's triggered ability won't trigger if you attack with multiple creatures and all but one of them are removed from combat.

Asari Captain — ruling 2

Asari Captain's triggered ability gives the solitary attacker +1/+0 for each creature you control that is either a Samurai or a Warrior as it resolves, including the attacker itself, if applicable. A creature that is both a Samurai and a Warrior is only counted once.

Asari Captain : règles, fonctionnement et interactions (MTG)

Asari Captain 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

Haste Whenever a Samurai or Warrior you control attacks alone, it gets +1/+0 until end of turn for each Samurai or Warrior you control.

How it works : Asari Captain

Original English text — Wizards of the Coast / Scryfall

#1February 18, 2022· Wizards of the Coast
A creature attacks alone if it's the only creature declared as an attacker during the declare attackers step. For example, Asari Captain's triggered ability won't trigger if you attack with multiple creatures and all but one of them are removed from combat.
No other card is named in this ruling.
#2February 18, 2022· Wizards of the Coast
Asari Captain's triggered ability gives the solitary attacker +1/+0 for each creature you control that is either a Samurai or a Warrior as it resolves, including the attacker itself, if applicable. A creature that is both a Samurai and a Warrior is only counted once.
No other card is named in this ruling.