Yarok, the Desecrated — ruling 1

Yarok affects a permanent's own enters-the-battlefield triggered abilities as well as other triggered abilities that trigger when that permanent enters the battlefield. Such triggered abilities start with "when" or "whenever."

Yarok, the Desecrated — ruling 2

Yarok's effect doesn't copy the triggered ability; it just causes the ability to trigger twice. Any choices made as you put the ability onto the stack, such as modes and targets, are made separately for each instance of the ability. Any choices made on resolution, such as whether to put counters on a permanent, are also made individually.

Yarok, the Desecrated — ruling 3

If a permanent entering the battlefield at the same time as Yarok (including Yarok itself) causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Yarok, the Desecrated — ruling 4

Abilities that apply "as [this creature] enters the battlefield," such as choosing a color with Diamond Knight, are also unaffected.

Yarok, the Desecrated — ruling 5

If a triggered ability is linked to a second ability, additional instances of that triggered ability are also linked to that second ability. If the second ability refers to "the exiled card," it refers to all cards exiled by instances of the triggered ability.

Yarok, the Desecrated — ruling 6

If you somehow control two Yaroks, a permanent entering the battlefield causes abilities to trigger three times, not four. A third Yarok causes abilities to trigger four times, a fourth causes abilities to trigger five times, and so on.

Yarok, the Desecrated — ruling 7

Replacement effects are unaffected by Yarok's ability. For example, a creature that enters the battlefield with one +1/+1 counter on it won't receive an additional +1/+1 counter.

Yarok, the Desecrated — ruling 8

You don't need to control the permanent entering the battlefield, only the permanent that has the triggered ability.

Yarok, the Desecrated : règles, fonctionnement et interactions (MTG)

Yarok, the Desecrated 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

Deathtouch, lifelink If a permanent entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

How it works : Yarok, the Desecrated

Original English text — Wizards of the Coast / Scryfall

#1July 12, 2019· Wizards of the Coast
Yarok affects a permanent's own enters-the-battlefield triggered abilities as well as other triggered abilities that trigger when that permanent enters the battlefield. Such triggered abilities start with "when" or "whenever."
No other card is named in this ruling.
#2July 12, 2019· Wizards of the Coast
Yarok's effect doesn't copy the triggered ability; it just causes the ability to trigger twice. Any choices made as you put the ability onto the stack, such as modes and targets, are made separately for each instance of the ability. Any choices made on resolution, such as whether to put counters on a permanent, are also made individually.
No other card is named in this ruling.
#3July 12, 2019· Wizards of the Coast
If a permanent entering the battlefield at the same time as Yarok (including Yarok itself) causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.
No other card is named in this ruling.
#4July 12, 2019· Wizards of the Coast
Abilities that apply "as [this creature] enters the battlefield," such as choosing a color with Diamond Knight, are also unaffected.
No other card is named in this ruling.
#5July 12, 2019· Wizards of the Coast
If a triggered ability is linked to a second ability, additional instances of that triggered ability are also linked to that second ability. If the second ability refers to "the exiled card," it refers to all cards exiled by instances of the triggered ability.
No other card is named in this ruling.
#6July 12, 2019· Wizards of the Coast
If you somehow control two Yaroks, a permanent entering the battlefield causes abilities to trigger three times, not four. A third Yarok causes abilities to trigger four times, a fourth causes abilities to trigger five times, and so on.
No other card is named in this ruling.
#7July 12, 2019· Wizards of the Coast
Replacement effects are unaffected by Yarok's ability. For example, a creature that enters the battlefield with one +1/+1 counter on it won't receive an additional +1/+1 counter.
No other card is named in this ruling.
#8July 12, 2019· Wizards of the Coast
You don't need to control the permanent entering the battlefield, only the permanent that has the triggered ability.
No other card is named in this ruling.
#9July 12, 2019· Wizards of the Coast
In some cases involving linked abilities, an ability requires information about "the exiled card." When this happens, the ability gets multiple answers. If these answers are being used to determine the value of a variable, the sum is used. For example, if Elite Arcanist's enters-the-battlefield ability triggers twice, two cards are exiled. The value of X in the activation cost of Elite Arcanist's other ability is the sum of the two cards' mana values. As the ability resolves, you create copies of both cards and can cast none, one, or both of the copies in any order.
No other card is named in this ruling.