Essence Symbiote — ruling 1

You gain 2 life when Essence Symbiote’s ability resolves, even if you can’t put a +1/+1 counter on the mutated creature (most likely because it’s left the battlefield).

Essence Symbiote — ruling 2

If Essence Symbiote mutates, its ability triggers.

Essence Symbiote : règles, fonctionnement et interactions (MTG)

Essence Symbiote 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

Whenever a creature you control mutates, put a +1/+1 counter on that creature and you gain 2 life.

How it works : Essence Symbiote

Original English text — Wizards of the Coast / Scryfall

#1April 17, 2020· Wizards of the Coast
You gain 2 life when Essence Symbiote’s ability resolves, even if you can’t put a +1/+1 counter on the mutated creature (most likely because it’s left the battlefield).
No other card is named in this ruling.
#2April 17, 2020· Wizards of the Coast
If Essence Symbiote mutates, its ability triggers.
No other card is named in this ruling.