Tranquilliser

Tranquilliser is one of 's ether Battle Arts in Xenoblade Chronicles. It puts one enemy to sleep.

Overview
The main purpose of tranq'ing an enemy is to temporarily remove them from the fight, so the party has an easier time working on the rest of the foes. In this sense, the art should pretty much be used as much as possible in order to maximize its uptime. This is even the case against single enemies, as even though the sleep is minimal, the guaranteed awakening crit is always useful. (Assuming it is not wasted on a weak art.) However, sleep is also quite good at dealing with visions, so it can also be worth holding onto it in case a bad one appears.

At high enough levels (level 8 technically, level 9 practically), Tranquilliser's effect time outstrips its cooldown, making it possible to lock an enemy asleep for as long as desired.