When Quicksmith Rebel enters, target artifact you control gains "{T}: This artifact deals 2 damage to any target" for as long as you control Quicksmith Rebel.
2017-02-09
If Quicksmith Rebel leaves the battlefield while its ability is on the stack, the artifact never gains the damage-dealing ability.
2017-02-09
If Quicksmith Rebel leaves the battlefield, you no longer control it.
2017-02-09
If Quicksmith Rebel or the artifact leaves the battlefield while the damage-dealing ability is on the stack, that ability resolves as normal.
2017-02-09
If another player gains control of Quicksmith Rebel, the artifact will no longer have the damage-dealing ability, even if you regain control of Quicksmith Rebel.