Daring Thief — ruling 1

The exchange of control lasts indefinitely. It doesn't expire when Daring Thief leaves the battlefield.

Daring Thief — ruling 2

Gaining control of an Aura or Equipment doesn't cause it to move, though gaining control of an Equipment will allow you to activate its equip ability to attach it to a creature you control later.

Daring Thief — ruling 3

The relevant card types (that is, the ones a nonland permanent can have) are artifact, battle, creature, enchantment, kindred, and planeswalker.

Daring Thief — ruling 4

If the full exchange can't happen, perhaps because one of the targets is illegal as the inspired ability tries to resolve, then nothing happens. No permanents change controllers.

Daring Thief — ruling 5

If another spell or ability allows you to change the targets of the ability (or perhaps copy it and choose new targets for the copy), you can change the targets only such that the final set of targets is still legal. For example, if the ability targets a creature you control and a creature an opponent controls, you couldn't change just the second target to a noncreature permanent controlled by that player. You could, however, change just the second target to a creature controlled by a different opponent. The two new targets can share a different card type than the two original targets did.

Daring Thief — ruling 6

Although the permanent you control can't be a land, the other target can, provided it shares a card type with the first target. For example, you could target an artifact you control and an artifact land controlled by an opponent.

Daring Thief — ruling 7

Inspired abilities trigger no matter how the creature becomes untapped: by the turn-based action at the beginning of the untap step or by a spell or ability.

Daring Thief — ruling 8

If an inspired ability triggers during your untap step, the ability will be put on the stack at the beginning of your upkeep. If the ability creates one or more token creatures, those creatures won't be able to attack that turn (unless they gain haste).

Daring Thief : règles, fonctionnement et interactions (MTG)

Daring Thief 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

Inspired — Whenever this creature becomes untapped, you may exchange control of target nonland permanent you control and target permanent an opponent controls that shares a card type with it.

How it works : Daring Thief

Original English text — Wizards of the Coast / Scryfall

#1April 26, 2014· Wizards of the Coast
The exchange of control lasts indefinitely. It doesn't expire when Daring Thief leaves the battlefield.
No other card is named in this ruling.
#2April 26, 2014· Wizards of the Coast
Gaining control of an Aura or Equipment doesn't cause it to move, though gaining control of an Equipment will allow you to activate its equip ability to attach it to a creature you control later.
No other card is named in this ruling.
#3April 26, 2014· Wizards of the Coast
The relevant card types (that is, the ones a nonland permanent can have) are artifact, battle, creature, enchantment, kindred, and planeswalker.
No other card is named in this ruling.
#4April 26, 2014· Wizards of the Coast
If the full exchange can't happen, perhaps because one of the targets is illegal as the inspired ability tries to resolve, then nothing happens. No permanents change controllers.
No other card is named in this ruling.
#5April 26, 2014· Wizards of the Coast
If another spell or ability allows you to change the targets of the ability (or perhaps copy it and choose new targets for the copy), you can change the targets only such that the final set of targets is still legal. For example, if the ability targets a creature you control and a creature an opponent controls, you couldn't change just the second target to a noncreature permanent controlled by that player. You could, however, change just the second target to a creature controlled by a different opponent. The two new targets can share a different card type than the two original targets did.
No other card is named in this ruling.
#6April 26, 2014· Wizards of the Coast
Although the permanent you control can't be a land, the other target can, provided it shares a card type with the first target. For example, you could target an artifact you control and an artifact land controlled by an opponent.
No other card is named in this ruling.
#7April 26, 2014· Wizards of the Coast
Inspired abilities trigger no matter how the creature becomes untapped: by the turn-based action at the beginning of the untap step or by a spell or ability.
No other card is named in this ruling.
#8April 26, 2014· Wizards of the Coast
If an inspired ability triggers during your untap step, the ability will be put on the stack at the beginning of your upkeep. If the ability creates one or more token creatures, those creatures won't be able to attack that turn (unless they gain haste).
No other card is named in this ruling.
#9April 26, 2014· Wizards of the Coast
Inspired abilities don't trigger when the creature enters the battlefield.
No other card is named in this ruling.
#10April 26, 2014· Wizards of the Coast
If the inspired ability includes an optional cost, you decide whether to pay that cost as the ability resolves. You can do this even if the creature leaves the battlefield in response to the ability.
No other card is named in this ruling.