Flame Skull
(Not Needed)
Stalking Blastbones → Morph of Blastbones
(Situational)
The reason you would use this skill is for “farming” corpses. Either morph will work, typically it would be Stalking for a Tank since it’s Magicka costing but if you are playing a Hybrid setup then you might use Blighted Blastbones. This skill is used primarily so you can create a corpse which you can then absorb with Necrotic Potency. When you combine this with other corpses it will increase the speed with which you gain back your Ultimate, which is very valuable with a setup designed for doing it.
Avid Boneyard → Morph of Boneyard
(Situational)
This is the selfish morph that creates a synergy that you can use yourself. This is only worth using if you don’t need the AoE Major Breach provided by the other morph and you want to give yourself the synergy for increasing your personal Alkosh uptime.
Unnerving Boneyard → Morph of Boneyard
(Vital)
Applies Major Breach as an AoE, plus provides your group with a synergy which does damage and heals you for the damage caused. This is the group morph, it’s good for trash fights for the Major Breach and it’s good for supplying a synergy to your group.
Skeletal Mage
(Situational)
This again would be used in a similar way to Blastbones and either morph could be used. The primary function is for creating corpses to absorb with Necrotic Potency for gaining back Ultimate faster. It will provide some additional DPS which would be good for a Hybrid setup. If you cast this skill halfway through its duration it will generate a corpse, so you don’t have to wait for it to die.
Mystic Siphon → Morph of Mystic Siphon
(Situational)
This skill can be used for the additional recovery but is a bit of a wasted skill slot just for 150 recovery. Might also be used when using Elemental Catalyst as this will be your source of damage over time Shock Damage. Using EC is generally not advised for a Tank other than very specific situations.