Following Silver Surfer's arrival as the herald of the so-called 'God of Light' who has been called Knull's opposite in King in Black #3, King in Black #4 goes one step further, fully identifying the 'God of Light.'
And as with Silver Surfer, who is implied to have had a hand in the original defeat of Knull by giving up his own 'light' in Silver Surfer: Black, the true 'God of Light' is a well-known – but somewhat more obscure – character/concept from the Marvel Universe.
Spoilers ahead for King in Black #4
As Dylan is consumed by Knull, a voice in his head urges him to defy Knull's control and use his power to counteract the symbiote "hive" that is engulfing heroes such as Cyclops, Johnny Storm, and Captain America.
Lashing out with anger over Eddie Brock being mortally wounded earlier in the story, Dylan reaches out and, with great difficulty, frees the previously named heroes from the "hive."
Rebuking Dylan and his power, Knull attempts a new attack, but he's met with psychic interference from the same voice that was in Dylan's head – that of Jean Grey of the X-Men, who unleashes her telepathic power on Knull to find his true ultimate weakness.
At first despairing over Knull's apparent lack of an Achilles' Heel, Jean discovers that the 'God of Light,' described as an "opposite force" that formed to counteract Knull's darkness (apparently different from that of Silver Surfer's 'light' that seeded life in the Marvel Universe and dispelled Knull's darkness in Silver Surfer: Black, or perhaps somehow born from it) is actually imprisoned on Earth.
Through Jean's psychic discovery of the 'God of Light,' Silver Surfer uses his apparent connection to the being to locate and free it, revealing once and for all what Knull's true opposite 'God of Light' is in the Marvel Universe – the mysterious Enigma Force, which turns those it possesses into the hero Captain Universe through one aspect of its power known as the Uni-Power.
Interestingly, Jean describes the Enigma Force/Uni-Power as a "symbiote of light."
Though Captain Universe has been a heroic identity all its own, other Marvel heroes such as Spider-Man have famously been possessed of its power over the years. In the 2007 limited series Captain Universe: Universal Power, numerous Marvel heroes take on the power of Captain Universe, including Silver Surfer.
In this case, the Enigma Force/Uni-Power apparently enters directly into the comatose body of Eddie Brock - potentially making him a new embodiment of Captain Universe, if not the 'God of Light' itself.
The story concludes in April 7's King in Black #5.
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