War Chest: Nightfall

You can’t use its coins for faceup maneuvers or to bolster it, but another unit or an eligible decree can grant it an action. Its attributes and restrictions still apply as normal (p. 2).

Discard one of that unit’s coins faceup from your hand and remove its Poison Counter. Unpoisoning is not a maneuver (p. 2).

No. If the counter is already on an enemy, move it to the newly poisoned unit; the previous unit is no longer poisoned (p. 2).

You can play it faceup as an action to return it beside its unit’s card, or use it for a facedown discard action such as initiative, recruit, or pass. You can’t use it for placement, a maneuver, unpoisoning, or proclaiming (p. 2).

Yes. Its attribute triggers when it controls any location, neutral or enemy; only its tactic is restricted to enemy-controlled locations (p. 2).