Boss Focus: Nightbane
In a Nutshell
The undead dragon Nightbane is accessible once you have completed an internal quest chain that starts with the quest Medivh’s Journal. Since Nightbane is a dragon, he will use a lot of typical dragon abilities, like Fear and Cleave.
The fight consists of two distinct phases that change back and forth depending on his hit points. The encounter will start around 30 seconds after someone used their Blackened Urn, when Nightbane will land on the the terrace and needs to be tanked during this ground phase. Whenever he loses 25% of his health points, he will take flight and the airborne phase will start and last for approximately 30 seconds.
Rundown
While on the ground, Nightbane will be more or less a tank and spank encounter. He will try to lay waste your maintank with three different abilities: standard melee attacks, cleaves and his Smoldering Breath. It may happen that those abilities follow shortly after each other, so be aware of possible damage spikes. Nightbane will cast Bellowing Roar periodically, just keep Fear Ward up whenever possible, and time your Renews and Prayers of Mending accordingly.
As soon as Nightbane’s health drops to 75%, 50% and 25%, he will take flight and hover over your raid. He will target a raid member and cast Rain of Bones on it, doing a bit of damage to that player and anyone close to him/her. As soon as this happens, 3 Restless Skeletons will spawn near the victim and attack anyone in the vicinity.
Nightbane is active and has an aggro list during the airborne phase. The list is cleaned on the beginning of the phase, though. Since all damage dealers are trying to kill off the Restless Skeletons during this phase, it will be the healers that will get Nightbane’s undivided attention. A few seconds after the skeletons have spawned, Nightbane will start to cast Smoking Blasts at the player on top of his aggro list. This will be a healer. If you are lucky and you have a Shaman or a Paladin healer with you, let them do the raid healing during this phase and you will be able to heal the damage they take in return by the Smoking Blasts. The paladin’s Righteous Fury ability helps a lot here.
If you are in risk of eating the Smoking Blast, be aware of it, and put up an Inner Fire in advance. It will save you from a lot of incoming damage since the Smoking Blast deals physical damage.
As soon as the airborne phase is about to end, move in position to heal your maintank that will grab the landing Nightbane and produce some aggro fast, since the landing is an aggro reset, too. Remember your Prayer of Mending, folks. It’s worth it’s weight in gold, an more. 
Watch out for
Be wary of the frequent aggro resets during this fight. Whenever Nightbane takes flight or lands, there will be a fresh and clean aggro list. Use Prayer of Mending and Fade wisely.
During the ground phase, Nightbane will sometimes cast Charred Earth on a random player not on top of the aggro list. Charred Earth creates a kind of void zone that anyone should move out of. The won’t kill you very fast, but they deal quite some damage if ignored. Spotting this AE zone is no problem, it’s very obvious.
When the airborne phase begins, try to get away from any Restless Skeletons near you. They don’t put much stress on a tank, but can rip a clothy apart with a few swings. Try to start low with healing during this phase, even if you are on raid healing duty. You won’t survive both, the skeletons and the dragon at once. 
Speaking of the dragon… watch out who is eating the Smoking Blasts. They are clearly to see as large red-and-black blobs raining from the sky. Anyone who is getting hit by them will lose health fast. Be prepared.
Healing Roles
While Nightbane is on the the ground, every healer will be on the maintank, trying to make the life of the other healers more comfortable. Don’t overheal, but be ready to counter some very spiky damage.
As soon as Nightbane is in the air, you need to assign one (or more) raid healer(s) and another healer that will take care of those healers. It’s best to use the healer with the highest physical damage reduction for raid healing, since he will be getting hit by the Smoking Blasts. As a priest, you will be the one in charge of covering the other healer’s backs, so watch their health and throw the raid a Prayer of Mending when possible.
Rewards
If every transition runs smoothly and your raid’s healers play mana sensitive, you should be facing a dead undead dragon after roughly 8 minutes. As a healing priest, you can try to get your hands on either the Emberspur Talisman, or the Nightstaff of the Everliving. Both very nice additions to your growing repertoire of stuff that helps you to keep stuff alive. 
