Except they aren’t absorbing, or drinking the Blood into their bodies. They aren’t draining creatures of blood, or hunting down prey with the goal of harvesting them for it either, which would be a cultural/societal aspect. They discovered the Blood pits the Trolls had made, and utilized it as a fuel. This does not mean they worship it, or that it somehow equates to their reverence for the Sunwell.
It’s not even about the “light” itself, its the fact that the Sunwell is made up between the Light, and Arcane, so it plays a major role in blood elf society, introducing themes like Death, or other chaotic elements is contrary to their society, and quite honestly contradictory to their development over the years. Liadrin wasn’t speaking for just herself when she speaks about the Sunwell, she’s speaking for the Blood elves as a whole, she’s the exposition mouthpiece for the player. She uses words like “us” and “we” when explaining the purpose of the Sunwell to the Nightborne while in the company of Lor’themar, and Rommath, I doubt she’d use this sort of rhetoric if it only applied to her and her Knights.
The Sunwell is the center of their society, it’s been described as much countless times, even lor’themar describes it as their people’s most sacred site, even Rommath, a mage is fiercely protective over it. The only example of a Blood elves who have openly defied or rejected the Sunwell became Void elves and joined the Alliance.
The point isn’t that the “light” is their only theme, merely that it’s a central one, and additional themes should compliment, or make sense, and not pop entirely out of left field with things like “Yeah by the way, remember those vampires who brutally murder Horde and Alliance alike? Yeah, they’re with the blood elves now.” or “remember the Fel elves who were willing to destroy the Sunwell, and fought to the bitter end to assist the Burning legion? Yeah, those mutated Blood elves are part of Blood elf society now.”
It makes no sense, and doesn’t line up with the Blood elf Narrative, or the direction they’ve been on for the last 10 years. Make it make sense, and don’t force feed the Blood elves fanfiction ideas because something they seem cool or edgy.
That is their stuff, and it’s been their stuff since their introduction into the game. Blood elves are a core race, they’re meant to act as a character template for the player to decide which walk of path that character might have chosen. Void elves are a themed, allied race who’s whole existence relies on the unique circumstances that led them to be Void elves. Void elves can get new, interesting themes without having to constantly dip their hands into the Blood elves’ visual kit over and over, and trying to justify it by saying they will have ombre characteristics is lazy, and tawdry.
And if you really think the helf crowd will be appeased with Ombre colors, and not just use it as another excuse or stepping stone toward solid colors than you’re either staggeringly naïve, or have just spent the last few years with your head firmly planted under the ground.
They don’t practice Blood magic, at least not in a traditional sense. Blood magic requires sacrifices, rituals, and well, death. The Blood elves are moreso Blood benders for the lack of a better phrase, utilizing it as a fuel, but they do not practice Blood magic in a sense where they’d worship Blood gods, or kill people to harvest it from them. They don’t imbibe or revere it like they do with the light, or the Arcane.
Ariel mentions their use of it in Nazmir, but they did not create those Blood pool, or practice any sort of “blood magic” we see the Blood trolls using, they simply channel it into their Constructs to fuel them.
