I thought undead don’t use the Light lore-wise because it burns them causing immense pain?
So how come Calia can walk around with a huge light dome and not get rekt by the Light? I think she even mentions she was raised by the Light?
… so then if that’s the case why can’t we have undead paladins? 
This. There was once a questline where she was resurrected by the Naaru after she was killed by Sylvanas for trying to reunite the undead with the living.
Because this game does NOT care about the lore. Hasn’t for YEARS.
She isn’t a forsaken undead who was raised by death magic.
She is a “lightforged” undead, who was raised by the light.
They are not the same. They are both undead, but two totally different things that power or keep them “alive”… one is being kept “alive” by death magic, the other by the light. This is also why she looks different than your regular run of the mill undead.
So in otherwords, she isn’t harmed by the light because she is literally of the light, granted life once again by a literal light Naruu with the aid of two of Azeroth’s most powerful priests of the light channeling light magic into her, plus she herself is a priest of the light, even before death.
She is the only lightforged undead, so “thats why” she can use holy magic.
Doest that explain the naxxramas horsemen that could also use holy magic even though he rwas raised by death magic? Not really.
And yes they were supposed to feel horrible when facing holy stuff. At least the ones raised by death i guess.
I mean at the end of the day she is a undead priest with the undead customization everyone wants for undead lol.
She was returned to life by the Light. She was Lightforged, thoroughly and totally infused and empowered with the Light.
Man, good thing they used this unique and wonderful power on a character that has had no relevance to the story and has never accomplished anything.
This has been debunked. But in short, yes. You are correct - Light and Death magic don’t play nice with one another. It’s still possible to weild the light as an undead, however, and there are multiple in-lore characters that prove it.
They just have to deal with the added level of pain.
Undead can already weild the light. But Calia is different altogether. She was reanimated in the light rather than in death. Necromancy can work with arcane, fel, light, void, and death as the catalyst.
Very juicy lore. The only thing I am uncertain is whether you can animate a corpse with Life magic or if such a feat is mathematically impossible.
this is explained just by the fact that undead can still use light magic. it just hurts them in the process, so the horseman was probably in pain as they cast each holy spell during the encounter, plus being empowered by the lich king or in the presence of Kel’thuzad probably also gave them the power to ignore or minimize the pain I’d imagine.
Gameplay purposes. Undead by and far can’t wield the light because it causes them immense pain and suffering. The exceptions are not the rule.
This is like arguing the semantics of void elf priests being holy spec. Its gameplay purposes and anyone with a brain should put 2 and 2 together.
Gameplay purpouses… for a NPC?
You sure not the guy solving 2+2 math problem LOL.
I mean its their right to make whatever lore or excuse they want to introduce or develop characters. But they never bother doing it either, its just “here take this, now make-up why we put here because we cant bother doing so” It would be cool having a storyline explaing such death knight or more holy-undead related stuff but we dont have it.
what are you talking about? she singlehandedly just essentially converted the Forsaken into an Alliance race in 9.2.5 
and converted characters such as Lillian Voss into an Alliance sympathizer and feel bad about killing her dad, etc…
tfw you realize the Forsaken is now led by an Alliance aligned character and her 2 converts, who she was killed in the first place, because she helped Forsaken defect from the Horde and to the Alliance and Sylvanas didn’t like that.
Because the writers at Blizzard think flash over substance and ignoring logic created by their own lore is ‘kewl’.
And they’re idiots.
Yeah, Lillian Voss, sure. We followed her around Scholomance when they remade that to be a part of… what, MOP? Some expansion where it made no sense to remake the dungeon.
So yeah Calia has done things no one else has ever done, she pretty much single-handed infiltrated the Horde and is now an Agent of the Alliance part of the Horde’s main Council of leaders, and in a major Horde race’s leadership Council. Something only SI:7 spies can only dream of, but she did it openly without any subterfuge.
plot armor
I like how she casually uses Light magic on regular Forsaken.
“The Light will protect you!”
sizzling intensifies
Krasus did it(specifically using Life according to the Novels) during The War of the Ancients Trilogy.
https://wowpedia.fandom.com/wiki/Alonsus_Faol
Muh lore.
lmao.
Light and void got retconned into stupid land - though I still do not accept it. I remember when the light was used to purge the wicked and the undead could not abide it.
Even in Shadowlands we have uther talk for all of two seconds about his lifetime of devotion to the light before OOOOoooh shiny blue thighladies. 