Urza, Lord High Artificer

When Urza, Lord High Artificer enters, create a 0/0 colorless Construct artifact creature token with "This creature gets +1/+1 for each artifact you control."
Tap an untapped artifact you control: Add {U}.
{5}: Shuffle your library, then exile the top card. Until end of turn, you may play that card without paying its mana cost.

Harbinger of the Seas

Back to Basics

Nonbasic lands don't untap during their controllers' untap steps.

Winter Moon

Players can't untap more than one nonbasic land during their untap steps.