Nightblade

Incapacitating Strike → Morph of Death Stroke
(Optional)
This is a good passive Ultimate to use on your front bar. If you tie it in with Siphoning Strikes then each Light and Heavy Attack will return a lot of resources. You need to know fights reasonably well for this however since you need to know exactly when it’s safe to use Light and Heavy Attacks. If you are experienced enough then this is a good additional resource tool you can use for a Nightblade.

Assassin’s Blade
(Unnecessary)
This could be used as a Nightblade Tank/DD Hybrid for doing damage otherwise not needed.

Lotus Fan → Morph of Teleport Strike
(Vital)
This is a gap closer which are rarely needed, but the main use of this skill is the Area of Effect Minor Vulnerability, you can Lotus Fan into an add stack to cause them all to take 5% more damage. This is a very good skill for add pulls, if you don’t have any other source of Minor Vulnerability in your group then you would need it on boss fights also but you have to be careful as it will cause you to drop block during the teleportation animation.

Mirage → Morph of Blur
(Vital/Situational)
This gives you Major Evasion which is great for any fights where you have to deal with Area of Effects it will reduce AoE damage by 25%, you also get Minor Resolve to increase your resistances slightly which will help for some high damage fights. You would use this morph when you need the additional resistances.

Phantasmal Escape → Morph of Blur
(Vital/Situational)
This is the other morph of Mirage, you lose the Minor Resolve which you sometimes really don’t need anyway, plus you can get Minor Resolve from Combat Prayer provided by the Healers. You gain immunity to snares and immobilisation and it will remove any that are already applied to you which makes this really strong for a lot of fights.

Mark Target
(Situational)
This can be used in any fights where you are range Tanking or want to pre apply Major Breach. Either morph would work but the one with a longer duration is probably better for a Tank.

Grim Focus
(Unnecessary)
This would be used as a Nightblade Tank/DD Hybrid for doing damage otherwise not needed.

Master Assassin
(Unnecessary)
Increased Weapon and Spell Damage is hardly noticeable as a Tank as you have such a low base starting value and you’ll rarely ever be flanking.

Executioner
(Optional)
This is a sustain passive which would be useful in add pulls or bosses with adds, its a difficult passive to make full use of however. You need to damage an enemy with an Assassination ability and the only real one a Tank would use is Lotus Fan but if a target dies 2 seconds after you used that ability you would restore Stamina.

Pressure Points
(Vital)
This is kind of the same as Master Assassin, its going to have a minor effect but it is worth stacking your Crit on a NB Tank as you need to cause Crit Damage to proc your group buff from the Hemorrhage passive.

Hemorrhage
(Vital)
This is the group buff you are expected to bring to a group. This is only useful for Stamina DDs and it will increase your groups Weapon Critical. To proc this passive you need to cause Crit damage which shouldn’t be too difficult when you have all of your abilities ticking on the target. If you have another Nightblade in a group then the NB Tank loses a lot of the functionality as this passive is one of the main and only reasons to use one.

Bolstering Darkness → Morph of Consuming Darkness
(Optional)
This is a passive Ultimate used for gaining an extra 2% Health. It can be good for emergency situations, reduces damage taken by 30% for everyone stood inside but you will usually be using Aggressive Horn.

Veiled Strike
(Not Needed)
Not used for Tanking.

Dark Cloak → Morph of Shadow Cloak
(Vital)
This is the Nightblade Tanks main heal. It gives a heal that is based off your Max Health meaning that you can quite easily be gaining 4-8k Healing per second if you are setup with high health, buffed up and you also get a crit heal. You gain Minor Protection when using this, and you also proc your Major Resolve via the Shadow Barrier passive by using this skill.

Refreshing Path → Morph of Path of Darkness
(Vital)
This skill is really nice for giving you and your group a speed boost at the cost of Magicka. It also does an AoE heal over time which can help if you are trying to control a situation with a lot of incoming damage, you can stack this with your Dark Cloak for more healing. You can also use this to proc certain gear sets if needed.

Mass Hysteria  → Morph of Aspect of Terror
(Vital)
This is your main Crowd Control ability that will fear enemies. Fearing is not as strong as immobilising as there is a period of CC immunity when you chain or fear an enemy so you won’t be able to do both actions quickly and smoothly like some other classes but it’s still a good way to stop adds or none Elite/Boss enemies doing any damage.

Dark Shade → Morph of Summon Shade
(Optional)
A nice skill to use when you have multiple targets as it causes AoE Minor Maim debuff which reduces enemies Damage by 5%. The spin attack that this does occurs around every 4 seconds and this is what causes the Minor Maim as an area effect. It’s also Magicka costing so you can use this rather than Heroic Slash if you are struggling for sustain.

Refreshing Shadows
(Vital)
Important Tank passive, the Magicka Recovery is nice, Health Recovery is ok and Stamina is generally useless.

Shadow Barrier
(Vital)
Basically a free way to obtain Major Resolve, when you cast a Shadow ability which is usually Dark Cloak, you gain Major Resolve and the time it lasts depends on how many Heavy Armor pieces you are using.

Dark Vigor
(Vital)
This is quite an important passive because it will boost Max Health. It’s important to reach high Max Health on the NB so that the Dark Cloak heal will do more healing as it is scaled with Max Health.

Dark Veil
(Vital)
Increases the duration of the heals coming from Dark Cloak and Refreshing Path and also increases the fear from Mass Hysteria so it’s a very important passive.

Soul Shred
(Unnecessary)
Could be slotted for the Magicka Flood and Soul Siphoner Passives but overall not really that useful.

Swallow Soul → Morph of Strife
(Vital)
The heal is not as strong from this as you get from Dark Cloak since it scales with Magicka but it will add to that incoming healing. As a Tank you might be able to heal around 2k with this, when combined with other sources its fine because you don’t have a burst heal you are relying on a variety of heals over time if they are needed. It provides some damage and the main use would be the Transfer passive which will help you generate quicker Ultimate.

Malevolent Offering
(Not Needed)

Cripple
(Not Needed)

Leeching Strikes → Morph of Siphoning Strikes
(Vital)
This is one of the best methods of sustain for a Nightblade Tank. It is quite difficult making full use of this, especially if you are a newer player since you need to Light Attack to get the most benefit. It also buffs your Heavy Attack resource gain so its worth having this skill running so you can benefit from the incoming Heavy Attack sustain when you get chance to do them. You also get a 4.2k Stamina restore when the ability ends so you should always try to let this run its full duration. In some rare situations you may want the other morph Siphoning Attacks if you lack Magicka sustain but you could just use Balance for that.

Power Extraction → Morph of Drain Power
(Situational)
This is an area of effect damage and debuff skill. The main issue is it costs Stamina to use it but it provides a small enemy debuff with Minor Cowardice so if you are struggling with certain adds you could use this.

Sap Essence → Morph of Drain Power
(Optional)
This is the other morph of Power Extraction but this morph heals rather than debuffing. It’s a decent skill since it does area of effect damage, the more enemies you hit, the more healing it does and it is an area of effect heal that heals your team so it can be a nice extra heal during add pulls.

Magicka Flood
(Vital)
You have quite a lot of Magicka abilities on a NB and you’ll usually gain this passive anyway.

Soul Siphoner
(Vital)
This is a small healing boost, you might as well use this passive and you’ll benefit from it just by slotting a Siphoning ability.

Transfer
(Vital)
Another Ultimate generating passive. You need to be casting a Siphoning ability every 4 seconds to gain the Ultimate from this, usually it would be Swallow Soul on Boss fights and Power Extraction/Sap Essence in add pulls.