Larekka

History Pre-Death
Forest Troll warrior. From northern Eastern Kingdoms, aka Lordaeron. Tribe formerly/currently of the Amani Trolls.

As the plague of undeath swept across Lordaeron, turning humans into scourge, the trolls were unaffected and attempted to take back some of their ancestral lands. However, the trolls would not have been blind to the devastation happening to the humans - although they saw it as an opportunity to take advantage of when the humans were weak, it is logical to assume they would also want to set up some sort of insurance against the plague coming to them and killing them off like the humans. This is how Larekka died.

Her tribe already worshipped several deities, and they saw the work of the scourge as that of a supernatural being; perhaps there was a loa they did not know of who guided them. And, the logical course of action when dealing with and attempting to appease a deity, is making offerings. The Gurubashi jungle trolls who worshipped hakkar would do sacrifices; if a god of blood wanted sacrifices, a god with plague and undeath would probably want sacrifices too. Therefore, in an attempt to protect the tribe, several memebers were sacrificed in a ritual designed to appease the unknown god(s) in the Necropolis that hung in the sky above their lands. Larekka was one of these sacrifices; as a seasoned and respected warrior she made a worthy sacrifice, along with several others of varying abilities and backgrounds. She gave her life willingly.

History as a Scourge DK
It was on a sacrificial altar that she was found by the scourge and brought to Acherus, along with those who were sacrificed with her. The ritual had not escaped the Lich King's notice, and the trolls were raised at his command. Larekka was the only one to survive both the raising and the training.

she's definitely a forest troll from lordaeron, from one of the tribes previously of the amani empire (possibly mossflayer, possibly not). If she had been a jungle troll from the south and the gurubashi empire, she would have been blood spec because of their worship of the god hakkar being their blood god (or would have completely rebelled and called them false or soemthing because hakkar is the blood god so how could they have power over blood without it being given by him... actually she probably would have seen the lich king as like, Hakkar reincarnated or something due to his dominion over blood and plague etc)

because trolls believe they get their magics etc from their loa, i've worked out that due to the nature of her creation and the fact that she'd be risen from death means she'd be following because she'd believe whoever created her to be a loa. the dk starting has them reporting to arthas, which yeah he's rather unholy but he has frostmourne being all prominent and frosty, so she'd naturally see him as possibly some sort of death/frost type god, especially with how all his minions revere him and kinda worship him, hence her going for frost spec - she thinks she's been chosen, basically, and is now some sort of high priestess working for him.

trolls have always communicated with the dead/spirits etc, a forsaken says as much in the Hinterlands, and considering the amani trolls didn't really blink at the scourge plague when it started as it just affected humans and instead they tried to take their lands back, and there's still a tribe in the western plaguelands, she wouldn't have been completely disgusted by undeath. Plus combined with thinking it's a gift from the loa = not upset. Also, a lot of what the scourge do with killing their enemies and infection and cannibalising etc is all things that aren't unfamiliar to her.

she's not unholy spec because there are trolls who are already necromancers and warlocks, and as a warrior she had chosen not to persue that path already.