Immobilized is a limb held fast. A wrestler’s grip closes on a forearm and does not let go; a net tangles a leg; a rope binds an arm to the body; a spell locks a hand rigid where it stands. Whatever the cause, the result is the same — the limb is still whole, still strong, still gripping whatever it was gripping, but it can no longer be moved.
The condition names the limb it applies to. A character can be immobilized in one arm and perfectly free in the other, and each such hold is recorded separately. It lasts exactly as long as whatever imposes it: when the grip is broken, the bindings cut, or the spell ends, the condition is removed and the limb is immediately free again.
Impediment
The affected limb cannot be moved. It may not strike, block, parry, gesture, or be brought to bear on anything, and any test that requires moving it fails.
Crucially, an immobilized limb does not drop what it is holding. Being held is not being disabled — the fingers still close, and a weapon in an immobilized hand stays in that hand. Taking it requires prising it loose, not merely pinning the arm. This is what distinguishes a hold from a disarm, and it is why a limb rendered unusable — by a grievous wound or a permanent maiming — is treated differently: an unusable limb is immobilized and loses its grip, and drops what it held. See Body Structure.
Physical Symptoms
Strain and growing ache in the pinned limb, numbness where a binding bites, and rapid fatigue in the muscles fighting the hold. A limb immobilized for a long time may be stiff and clumsy for a while after it is released.
Emotional Distress
Panic at being unable to answer a threat with a hand that will not move, and — for a fighter used to relying on both arms — the particular dread of being worked on at leisure by an opponent who has taken away half the defence.