You may choose not to untap this artifact during your untap step. , : Tap target creature. It doesn't untap during its controller's untap step for as long as this artifact remains tapped.
Not legal in Standard, Pauper, Historic, Timeless, Alchemy, Brawl, Standard Brawl, Pauper Commander, Gladiator, Premodern, Pre-EDH, Old School
Notes & Rules Information
The activated ability can target any creature, not just one that's untapped.
(2014-04-26)
As long as Deserter's Quarters remains tapped, the effect stopping the creature from untapping during its controller's untap step remains even if that creature untaps some other way (for example, with Colossal Heroics).
, 
: Tap target creature. It doesn't untap during its controller's untap step for as long as this artifact remains tapped.