Warden of the First Tree — ruling 1

Neither the first nor the second ability has a duration. If one of them resolves, it will remain in effect until Warden of the First Tree leaves the battlefield or some subsequent effect changes its characteristics.

Warden of the First Tree — ruling 2

The first and second activated abilities cause Warden of the First Tree to lose any other creature types it has. It retains any card types or supertypes it may have.

Warden of the First Tree — ruling 3

The first ability overwrites any previous effects that set the creature's base power and toughness to specific values. Any power- or toughness-setting effects that start to apply after the first ability resolves will overwrite this effect.

Warden of the First Tree — ruling 4

Effects that modify Warden of the First Tree's power or toughness, such as the one created by Titanic Growth, will apply to Warden of the First Tree no matter when they started to take effect. The same is true for any +1/+1 counters on Warden of the First Tree and effects that switch its power and toughness.

Warden of the First Tree : règles, fonctionnement et interactions (MTG)

Warden of the First Tree 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

: This creature becomes a Human Warrior with base power and toughness 3/3. : If this creature is a Warrior, it becomes a Human Spirit Warrior with trample and lifelink. : If this creature is a Spirit, put five +1/+1 counters on it.

How it works : Warden of the First Tree

Original English text — Wizards of the Coast / Scryfall

#1November 24, 2014· Wizards of the Coast
Neither the first nor the second ability has a duration. If one of them resolves, it will remain in effect until Warden of the First Tree leaves the battlefield or some subsequent effect changes its characteristics.
No other card is named in this ruling.
#2November 24, 2014· Wizards of the Coast
The first and second activated abilities cause Warden of the First Tree to lose any other creature types it has. It retains any card types or supertypes it may have.
No other card is named in this ruling.
#3November 24, 2014· Wizards of the Coast
The first ability overwrites any previous effects that set the creature's base power and toughness to specific values. Any power- or toughness-setting effects that start to apply after the first ability resolves will overwrite this effect.
No other card is named in this ruling.
#4November 24, 2014· Wizards of the Coast
Effects that modify Warden of the First Tree's power or toughness, such as the one created by Titanic Growth, will apply to Warden of the First Tree no matter when they started to take effect. The same is true for any +1/+1 counters on Warden of the First Tree and effects that switch its power and toughness.
No other card is named in this ruling.