Warlocks and Rapid Shot, And Gear Questions

[Falling Icicle]

My question is whether or not Hellfire Blast counts as an Essence invocation when it comes to Eldritch Blast. While the class lists Hellfire blast as a special ability, I'm rather curious if it's possible to mix other Essence invocations into a Hellfire Blast.

Rather, should Hellfire Blast count as the essence invocation whenever you use it? Or are you allowed to cast Hellfire Blast mixed with the Virtrolic Essence Invocation as well as say, Eldritch Chain?

Thanks in advance.

A strict reading of the rules would seem to indicate that it is an eldritch essence invocation. It uses the same wording - "changes your eldritch blast into (x)." However, I encourage you to ignore this, as it would make the ability worthless. You could get more damage out of Vitriolic Blast (albeit overtime), and without spending a point of Con, not to mention 3 levels.