Covenants
Best covenant/soulbind for Single target: Kyrian Pelagos*
Best covenant/soulbind for Dungeons/AoE: Necrolords Emeni
*Kyrian Pelagos requires full Renown to really pull far ahead of the competing Covenants because it is one of the few soulbinds that has a dps node at both the start and the end of the soulbind tree. You can pick any of the covenants at the start of expansion and be competitive. Each of them has certain areas/fights where they pull ahead due to their conduit tree, their utility or the covenant ability. Then once you have enough renown you can swap to Kyrian Pelagos.
Soulbinds and Conduits
Conduits Overview
Single Target: Dissonant Echoes / Haunting Apparitions
If you use the Talbadar’s Stratagem legendary: Dissonant Echoes / Mind Devourer
Spread Cleave: Dissonant Echoes / Haunting Apparitions
If you’re not using the Auspicious Spirits talent: Dissonant Echoes / Mind Devourer
If you’re using mostly Mind Sear: Mind Devourer / Haunting Apparitions
If you’re using Searing Nightmare and Mindbender: Mind Devourer / Rabid Shadows
Legendaries
Currently, there are 2 legendaries that are competitive for shadow.
Eternal Call to the Void: This gives your spells a chance to spawn a void tentacle that will attack your target, dealing damage and generating insanity.
Talbadar’s Stratagem: This increases the damage of your Mind Blasts by 60% if Vampiric Touch, Shadow Word: Pain and Devouring Plague are on the target.
Eternal Call to the Void is currently the best legendary overall. Talbadar’s Stratagem might see some use in spread cleave situations when combined with the Psychic Link talent.
Gear
Currently, the Cabalist’s Hymnal trinket (especially if you have people in your party who are also using it) from the raid look very good.