Gurmag Drowner — ruling 1

A creature with exploit “exploits a creature” when the controller of the exploit ability sacrifices a creature as that ability resolves.

Gurmag Drowner — ruling 2

You choose whether to sacrifice a creature and which creature to sacrifice as the exploit ability resolves.

Gurmag Drowner — ruling 3

You can sacrifice the creature with exploit if it’s still on the battlefield. This will cause its other ability to trigger.

Gurmag Drowner — ruling 4

If the creature with exploit isn’t on the battlefield as the exploit ability resolves, you won’t get any bonus from the creature with exploit, even if you sacrifice a creature. Because the creature with exploit isn’t on the battlefield, its other triggered ability won’t trigger.

Gurmag Drowner — ruling 5

You can’t sacrifice more than one creature to any one exploit ability.

Gurmag Drowner : règles, fonctionnement et interactions (MTG)

Gurmag Drowner 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

Exploit (When this creature enters, you may sacrifice a creature.) When this creature exploits a creature, look at the top four cards of your library. Put one of them into your hand and the rest into your graveyard.

How it works : Gurmag Drowner

Original English text — Wizards of the Coast / Scryfall

#1February 25, 2015· Wizards of the Coast
A creature with exploit “exploits a creature” when the controller of the exploit ability sacrifices a creature as that ability resolves.
No other card is named in this ruling.
#2February 25, 2015· Wizards of the Coast
You choose whether to sacrifice a creature and which creature to sacrifice as the exploit ability resolves.
No other card is named in this ruling.
#3February 25, 2015· Wizards of the Coast
You can sacrifice the creature with exploit if it’s still on the battlefield. This will cause its other ability to trigger.
No other card is named in this ruling.
#4February 25, 2015· Wizards of the Coast
If the creature with exploit isn’t on the battlefield as the exploit ability resolves, you won’t get any bonus from the creature with exploit, even if you sacrifice a creature. Because the creature with exploit isn’t on the battlefield, its other triggered ability won’t trigger.
No other card is named in this ruling.
#5February 25, 2015· Wizards of the Coast
You can’t sacrifice more than one creature to any one exploit ability.
No other card is named in this ruling.