Free action: knowledge check. Relaying via telepathy.
Free action: 5 ft step Dark companion remains in previous square. Elemental A receives -2 to AC and saves
Swift action: Hexblade's Curse on Grave Elemental A and C (Twin Curse feat allowing two creatures within 10 ft of each other to be effected.) DC 19 Will save or 2 penalty on attacks, saves, ability checks, skill checks and weapon damage rolls for 1 hour
Free action: Eldritch Beam
Eldritch Beam Originally Eldritch Glaive; DM 82
Least; 2nd [Blast Shape]
This blast shape invocation gives your eldritch blast physical substance, forming a long glowing beam similar to a glaive that you wield with both hands. As a free action that does not provoke an attack of opportunity, you can form an eldritch beam until the start of your next turn. As a full-round action, you can make a number of melee touch attacks as your base attack bonus allows as if wielding a reach weapon. If you hit, your target is affected as if struck by your eldritch blast (including any eldritch essence applied to the eldritch beam). While wielding your eldritch beam, you also threaten nearby squares as if wielding a reach weapon, and you can make attacks of opportunity with your eldritch beam (these are also melee touch attacks). Eldritch beam cannot be applied to an Eldritch Volley eldritch blast.
Full attack (2 attacks) on Elemental A with the Eldritch Beam. This triggers Dreadful Wrath. Elementals A and C are within 20 ft, so they must Will save vs DC 19 or be Shaken
Each successful attack with the weapon-like effect forces a DC 22 Will save for Beshadowed Blast or be blinded for one round