Who is Titan the deadliest Hulk and what the heck is "Starship Hulk"?

gamesradar.com:

Hulk's "deadliest" incarnation Titan makes his highly-anticipated debut in April 20's Hulk #6 from writer Donny Cates and artist Ryan Ottley, breaking forth and setting up the upcoming Hulk vs. Thor: Banner of War. 

But who or what is Titan, and how does he arrive in the Hulk's story? And perhaps most importantly, how does Titan's emergence relate to the current 'Starship Hulk' storyline? 

We'll explain what Titan actually is and how he emerges from the Hulk momentarily, but first, we need to explain what 'Starship Hulk' actually is and how the current relationship between Bruce Banner and the Hulk actually works.

As established at the start of the current volume of Hulk, Bruce Banner has managed to splinter and separate his own consciousness and personality from that of the Hulk, with both Banner and Hulk co-existing inside Hulk's body. 

Using an unrevealed combination of magic, science, and psychic abilities - including surgically implanted cybernetic components - Banner has turned Hulk's body into a mere vessel which he literally pilots from a psychically constructed cockpit that exists in Banner and Hulk's combined psyche, and which allows Bruce Banner's mind to be in control over the power contained in Hulk's body - kinda Pacific Rim mech-suit style, but with the good old fashioned green Hulk body in place of a mech.

Unlike past eras in which Hulk and Banner co-existed or in which Banner's intelligence was maintained into his Hulk transformations, Banner's mind exists wholly separately from Hulk's mind, with Hulk's essence trapped in what Banner calls the "Engine Room," a kind of psychic version of the X-Men's Danger Room that fuels the Hulk body's strength by constantly forcing the Hulk's consciousness to battle