When Zhonya's Hourglass is played from hidden, must it target a unit at the battlefield where it was hidden?

Ruling: No, Zhonya's Hourglass is not restricted to targeting units at the battlefield where it was hidden because it does not target. The hidden targeting restriction only applies to cards that actually target.

Nuances:

• The rule about hidden spells having an additional "here" targeting requirement only applies to cards that target
• Zhonya's Hourglass is gear that does not target, so this restriction does not apply to it
• The future rules will clarify that the restriction only applies to targeting