GURPSよろず

Only advantages that affect others can have this limitation.
Your ability manipulates an existing item or condition, which must touch or surround the target. Unlike Accessibility, this doesn’t affect activation – you can trigger your ability anywhere, barring a failed roll or another limitation.
However, your ability is only effective if the subject is in a particular environment . . . and the GM can alter its effects if the environment you’re attempting to manipulate is at all unusual.

Example: A Binding that commands plants to entangle the victim would do nothing in an area without vegetation.
It would be little more than a nuisance if the only plant nearby were a small potted fern . . . and totally unpredictable in an alien jungle!
The GM should base the value on the environment’s rarity:

Very Common: Environment is present all the time, outside of one or two unusual situations that would be difficult for an enemy to arrange; e.g., in a gravity field, in the presence of air,
or on a planet. -5%.

Common: Environment is present most of the time, but a resourceful foe could arrange for it to be absent; e.g., in contact with dust or in the presence of microbes. -10%.

Occasional: Environment is often absent, or easily avoided by enemies (although a crafty user might be able to “rig” an important encounter to work around this); e.g., in a city, in the wilderness, outdoors, or touching the ground. -20%.

Rare: Environment is usually absent and difficult for the user to arrange; e.g., in a storm, in dense vegetation, in the desert, or underground.-40%.

Very Rare: Environment is so unlikely that the ability is useless most of the time; e.g., in lava, in quicksand, or in vacuum. -80%.

The GM should forbid proposed Environmental limitations that duplicate one of the ability’s built-in restrictions; e.g., “in the water” isn’t valid for Control (Water).
In games with powers, an ability that gets -10% for a mundane countermeasure or insulator as part of its power modifier already has this limitation – don’t apply it a second time.