Atzocan Archer — ruling 1

You must choose another target creature (if able) as Atzocan Archer’s triggered ability is put on the stack. You choose as that ability resolves whether those creatures fight.

Atzocan Archer — ruling 2

If Atzocan Archer isn’t on the battlefield as its triggered ability resolves, or if the target of that ability is illegal, no creature will deal or be dealt damage.

Atzocan Archer — ruling 3

Atzocan Archer’s ability can target another creature you control (such as a Dinosaur with an enrage ability).

Atzocan Archer : règles, fonctionnement et interactions (MTG)

Atzocan Archer 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

Reach When this creature enters, you may have it fight another target creature. (Each deals damage equal to its power to the other.)

How it works : Atzocan Archer

Original English text — Wizards of the Coast / Scryfall

#1September 29, 2017· Wizards of the Coast
You must choose another target creature (if able) as Atzocan Archer’s triggered ability is put on the stack. You choose as that ability resolves whether those creatures fight.
No other card is named in this ruling.
#2September 29, 2017· Wizards of the Coast
If Atzocan Archer isn’t on the battlefield as its triggered ability resolves, or if the target of that ability is illegal, no creature will deal or be dealt damage.
No other card is named in this ruling.
#3September 29, 2017· Wizards of the Coast
Atzocan Archer’s ability can target another creature you control (such as a Dinosaur with an enrage ability).
No other card is named in this ruling.