Banish

Banish
Banish 30 yd range 8% of base mana 1.5 sec cast Banishes the enemy target, preventing all action but making it invulnerable for up to X sec. Only one target can be banished at a time. Only works on Demons and Elementals.
Usable by
Class	Warlock
Properties
Type	Defensive
School	Shadow
Cooldown	None/Global Cooldown
Other information
Ranks	2
Related debuff
Magic Banish Invulnerable, but unable to act. Duration: X seconds

Banish is a Shadow-based crowd control spell which causes an elemental or demon to become invulnerable for a period of time.

Rank table

Rank	Level	Duration	Cost
1	28	20 sec	45
2	48	30 sec	1 26

Despite that Banish is considered a Magic effect; it cannot be dispelled.
Damage over time effects applied to the target who is affected by Banish will continue to count down but will cause zero damage.

If you are having trouble because Banish keeps breaking early then try casting Curse of the Elements first. Doing this will cause there to be a much improved chance that Banish will last its full duration.
Note that the single difference between ranks is the duration. Using a lower rank is possible, and handy too, if you are having to wait oftentimes for a longer version of Banish to fade.
Banished mobs are effected by a Voidwalker's Torment and Suffering abilities (and possibly the similar hunter pet ability as well?).
Mobs can be Taunted during a Banish. Communicate to your tank when the effect is seconds away from wearing off, they will appreciate the notice as it will allow them to place a Taunt effect on the mob and keep it from running out of melee range.
As with other Crowd Control abilities, it can be useful to employ the "Focus" system, especially with a macro such as this one.
If you cast Banish two times on the same target then the effect will end.

May be used against on another warlock's minion.
May be used on elementals such as a Mage's Water Elemental, a Shaman's Fire and Earth Elementals, and a Druid in Tree of Life form.
May be used against warlocks under the transformative effects of Metamorphosis.