Nyxborn Shieldmate — ruling 1

On the stack, a spell with bestow is either a creature spell or an Aura spell. It's never both, although it's an enchantment spell in either case.

Nyxborn Shieldmate — ruling 2

Unlike other Aura spells, an Aura spell with bestow isn't countered if its target is illegal as it begins to resolve. Rather, the effect making it an Aura spell ends, it loses enchant creature, it returns to being an enchantment creature spell, and it resolves and enters the battlefield as an enchantment creature.

Nyxborn Shieldmate — ruling 3

Unlike other Auras, an Aura with bestow isn't put into its owner's graveyard if it becomes unattached. Rather, the effect making it an Aura ends, it loses enchant creature, and it remains on the battlefield as an enchantment creature. It can attack (and its {T} abilities can be activated, if it has any) on the turn it becomes unattached if it's been under your control continuously, even as an Aura, since your most recent turn began.

Nyxborn Shieldmate — ruling 4

If a permanent with bestow enters the battlefield by any method other than being cast, it will be an enchantment creature. You can't choose to pay the bestow cost and have it become an Aura.

Nyxborn Shieldmate — ruling 5

Auras attached to a creature don't become tapped when the creature becomes tapped. Except in some rare cases, an Aura with bestow remains untapped when it becomes unattached and becomes a creature.

Nyxborn Shieldmate : règles, fonctionnement et interactions (MTG)

Nyxborn Shieldmate 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

Bestow (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached.) Enchanted creature gets +1/+2.

Complete guide

Nyxborn Shieldmate is a versatile card from the Theros block that showcases the Bestow mechanic, allowing it to serve as either a combat trick or a reliable creature. Whether you need an early blocker or a buff for your commander, this Human Soldier provides resilience in the face of removal.

What It Does

Nyxborn Shieldmate is an Enchantment Creature that can be cast for its regular mana cost of one White mana to enter as a 1/2 creature. Alternatively, you can pay its Bestow cost of {2}{W} to cast it as an Aura spell. While it is an Aura, it grants the enchanted creature a +1/+2 power and toughness boost. If the creature it is attached to leaves the battlefield, Nyxborn Shieldmate doesn't go to the graveyard; instead, it falls off and stays on the battlefield as a creature.

How it Resolves Step by Step

When you cast Nyxborn Shieldmate for its Bestow cost, you choose a creature as a target. On the stack, it is an Aura spell and not a creature spell. As it resolves, it enters the battlefield attached to that creature. If the target becomes illegal before the spell resolves (for example, if the creature is destroyed in response), the Bestow spell stops being an Aura and becomes a creature spell again. It then resolves as an Enchantment Creature, entering the battlefield rather than being countered like a normal Aura would be.

Common Mistakes

A frequent error is trying to Cheat the Bestow cost using effects that put permanents directly onto the battlefield. If Nyxborn Shieldmate enters the battlefield without being cast (such as through a reanimation effect), it must enter as a creature. You can only choose to make it an Aura if you are casting it and paying the Bestow cost. Additionally, remember that while the Aura doesn't tap when the enchanted creature taps, it will only be able to attack the turn it becomes a creature if you have controlled the permanent since the start of your turn.

When to Play It

Play Nyxborn Shieldmate for its Bestow cost when you want to protect a key creature from damage-based removal or to win a combat exchange. Because it stays on the board after the enchanted creature dies, it provides excellent insurance against 'one-for-one' trades, ensuring you still have a board presence after a board wipe or a removal spell hits your primary threat.

Interaction examples

Boosting Utility

Esper Sentinel

If you Bestow Nyxborn Shieldmate onto Esper Sentinel, the Sentinel's power increases to 2. This forces your opponent to pay {2} instead of {1} to prevent you from drawing cards whenever they cast their first noncreature spell. If the Sentinel is eventually destroyed, the Shieldmate remains on the battlefield as a 1/2 creature to continue your defense.

Building a Defensive Flyer

Ornithopter of Paradise

You can cast Nyxborn Shieldmate for its Bestow cost targeting Ornithopter of Paradise. This turns your mana-producer into a 1/4 Flying creature, making it a much more effective blocker against small attackers. If an opponent uses a removal spell on the Ornithopter, Nyxborn Shieldmate simply drops onto the battlefield as a creature, ensuring you don't lose two cards' worth of value to a single removal spell.

Guide written with AI from the official text and rulings. Official English text prevails.

How it works : Nyxborn Shieldmate

Original English text — Wizards of the Coast / Scryfall

#1September 15, 2013· Wizards of the Coast
On the stack, a spell with bestow is either a creature spell or an Aura spell. It's never both, although it's an enchantment spell in either case.
No other card is named in this ruling.
#2September 15, 2013· Wizards of the Coast
Unlike other Aura spells, an Aura spell with bestow isn't countered if its target is illegal as it begins to resolve. Rather, the effect making it an Aura spell ends, it loses enchant creature, it returns to being an enchantment creature spell, and it resolves and enters the battlefield as an enchantment creature.
No other card is named in this ruling.
#3September 15, 2013· Wizards of the Coast
Unlike other Auras, an Aura with bestow isn't put into its owner's graveyard if it becomes unattached. Rather, the effect making it an Aura ends, it loses enchant creature, and it remains on the battlefield as an enchantment creature. It can attack (and its abilities can be activated, if it has any) on the turn it becomes unattached if it's been under your control continuously, even as an Aura, since your most recent turn began.
No other card is named in this ruling.
#4September 15, 2013· Wizards of the Coast
If a permanent with bestow enters the battlefield by any method other than being cast, it will be an enchantment creature. You can't choose to pay the bestow cost and have it become an Aura.
No other card is named in this ruling.
#5September 15, 2013· Wizards of the Coast
Auras attached to a creature don't become tapped when the creature becomes tapped. Except in some rare cases, an Aura with bestow remains untapped when it becomes unattached and becomes a creature.
No other card is named in this ruling.