Ghosthelm Courier 

Creature — Human Wizard
You may choose not to untap this creature during your untap step.
,
: Target Wizard creature gets +2/+2 and has shroud for as long as this creature remains tapped. (It can't be the target of spells or abilities.)
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyLEGALvintageLEGALcommanderLEGAL