Can Hidden units affect units on other battlefields?

Ruling: Hidden units and spells played from Hidden must target units at the same battlefield they were played from unless explicitly stated otherwise. Effects that don't target are not restricted by battlefield. Units must be played to the battlefield where the Hidden unit was played from.

Sequence:

• When a Hidden unit or spell is played, identify which battlefield it was played from
• Any targeting effects must target units at that same battlefield
• Any units played must be played to that same battlefield
• Non-targeting effects can affect any battlefield

Nuances:

• Effects that explicitly state they can target other locations (like Tideturner's play effect) override this restriction
• Non-targeting effects like global buffs (Stand United's buff enhancement) or replacement effects (Zhonya's Hourglass) are not restricted by battlefield