Cartouche of Strength — ruling 1

If the triggered ability's target is illegal when it tries to resolve, or if the enchanted creature has left the battlefield, no creature will deal or be dealt damage.

Cartouche of Strength — ruling 2

The enchanted creature has +1/+1 and trample while it's fighting. However, trample doesn't apply during a fight.

Cartouche of Strength — ruling 3

If Cartouche of Strength leaves the battlefield before its triggered ability resolves, the creature it last enchanted will fight the target creature if it's still on the battlefield at that time. However, it won't have +1/+1 from Cartouche of Strength anymore.

Cartouche of Strength — ruling 4

Cartouche is an enchantment subtype with no special meaning. Other cards may care about which enchantments are Cartouches.

Cartouche of Strength — ruling 5

If the target creature becomes an illegal target before a Cartouche spell resolves, the spell doesn't resolve. It doesn't enter the battlefield.

Cartouche of Strength — ruling 6

Each Cartouche is an Aura with "Enchant creature you control." If another player gains control of either the Cartouche or the enchanted creature (but not both), then the Cartouche will be enchanting an illegal permanent and be put into its owner's graveyard as a state-based action.

Cartouche of Strength : règles, fonctionnement et interactions (MTG)

Cartouche of Strength 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

Enchant creature you control When this Aura enters, you may have enchanted creature fight target creature an opponent controls. (Each deals damage equal to its power to the other.) Enchanted creature gets +1/+1 and has trample.

How it works : Cartouche of Strength

Original English text — Wizards of the Coast / Scryfall

#1April 18, 2017· Wizards of the Coast
If the triggered ability's target is illegal when it tries to resolve, or if the enchanted creature has left the battlefield, no creature will deal or be dealt damage.
No other card is named in this ruling.
#2April 18, 2017· Wizards of the Coast
The enchanted creature has +1/+1 and trample while it's fighting. However, trample doesn't apply during a fight.
No other card is named in this ruling.
#3April 18, 2017· Wizards of the Coast
If Cartouche of Strength leaves the battlefield before its triggered ability resolves, the creature it last enchanted will fight the target creature if it's still on the battlefield at that time. However, it won't have +1/+1 from Cartouche of Strength anymore.
No other card is named in this ruling.
#4April 18, 2017· Wizards of the Coast
Cartouche is an enchantment subtype with no special meaning. Other cards may care about which enchantments are Cartouches.
No other card is named in this ruling.
#5April 18, 2017· Wizards of the Coast
If the target creature becomes an illegal target before a Cartouche spell resolves, the spell doesn't resolve. It doesn't enter the battlefield.
No other card is named in this ruling.
#6April 18, 2017· Wizards of the Coast
Each Cartouche is an Aura with "Enchant creature you control." If another player gains control of either the Cartouche or the enchanted creature (but not both), then the Cartouche will be enchanting an illegal permanent and be put into its owner's graveyard as a state-based action.
No other card is named in this ruling.