after several years of peace and quiet this page is getting passed around once more with the suggestion that it depicts a ‘grimdark’ Eridan. it doesn’t; he’s normal 7 pages beforehand and looks perfectly fine 6 pages later. but the fact that enough people thought of Rose’s grimdark phase when they saw this panel means I should probably at least consider that a deliberate allusion was being made here.
it has been suggested the 'grimdark’ colour scheme being used here is to suggest that Eridan is ideologically grimdark, or in a grimdark state of mind. the fundamental assumption in this case is that grimdarkness is malevolence, which is demonstrably untrue. the very origin of grimdarkness is in moral ambiguity; grimdark Rose was not in touch with malevolent forces, but merely forces with their own agenda in opposition to the destruction of reality. Eridan, of course, has his own agenda; but there is no such ambiguity in his. his intentions are purely ill-willed.
the truth is that there is a troll who went 'grimdark’. her name just happens to be Kanaya.
there can be no suggestion that a troll might deviate from their path by aligning with forces nocturnal and needlessly-dramatic. trolls are by their very nature nocturnal and dramatic. Rose’s transformation, the touch of dark gods cloaking her body in shadow, evokes Problem Sleuth’s undead creatures of indeterminate alignment. to suit their photophobic nature, the bugbears of Alternian lore are instead vampires bathed in a white glow.
Kanaya choosing a wizard of white science to play rival to Rose’s dark magic exemplifies this mirror relationship. Eridan was never in the running to be the grimdark troll. so the purpose of the infamed 'grimdark Eridan panel’ should understood as expressing his connection to the true grimdark troll, Kanaya.
a rainbow drinker is a vampire that feeds on blood and daylight, and much commentary has been made on the kiss from a knight of blood that preceded Kanaya’s transformation; but relatively little attention has gone to the blast of light that kicked it all off. to 'fill someone with daylight’ is an old euphemism for riddling them with bullet holes, which seems fitting in the circumstances; and in fact it got some mileage in Problem Sleuth, where our zombie and vampire plagues started off. so let’s take another quick look back in that direction.
Mobster Kingpin’s FILL 'EM WITH DAYLIGHT comb rave is, put plainly, a hope blast. but it is such a hope blast that it tears a rift open in spacetime. to strengthen the connection to Eridan’s blast; opening these kinds of rifts in space is the specific purpose of a wand! Calliope uses her wand to open up black holes, like the one she spent Act 6 hiding in and the one she opens in Act 7 to swallow up the green sun, and Echidna, who herself lives in a burrow that appears as a rift into the void, bestows upon her heroes the quills needed to Scratch reality.
just as Calliope uses her wand to turn the black hole symbol on her chest into a real vortex, Eridan’s blast turns Kanaya into a rainbow drinker by opening a rift in her guts. fittingly, a black hole, as a singularity from which light cannot escape, is the ultimate 'rainbow drinker’; a piece of trivia alluded to when Mobster Kingpin’s black hole absorbs the sun, “filling it with daylight.”