Ghosthelm Courier is a uncommon Creature — Human Wizard card from Onslaught (ONS), collector number 85. Current market price: $0.19 (foil $0.51), TCGplayer market prices via Scryfall.
You may choose not to untap this creature during your untap step. {2}{U}, {T}: 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.)