Alivia Sureka

Alivia Sureka is one of the few perpetuals in the galaxy, as well as being one of the least grimdark characters in the grim darkness of the far future. She also happens to be the Emperor's Waifu, and much like himself, she is a total badass, when she gets the chance to show off her skills, which is not very often (in fact we only have two accounts of her feats, one of which ended with her getting impaled by Horus...)

History

Not much is known of her history, other than she is one of the perpetuals to have traveled with Emps to the planet Molech during the Dark Age of Technology, where he stepped through a warp portal and acquired all his knowledge about gene modifications and the like. He then subsequently abandoned her there to watch over the portal while he got a one-way ticket back to Terra. She is younger than the Emperor by about 9000 years, which still makes her old as fuck, but much easier to relate to; since she spent her first years in the 20th and 21st century on Terra, she regularly speaks using modern English slang and abbreviations (Despite being born in Denmark...(It actually makes sense as Danish people use a lot of English slang and words)). Apparently she really liked this era, as she carries around various items that we could easily walk down the street and find today, including a book of Hans Christian Andersen's fairytales, because apparently no one has written a better book in thirty thousand years.

When Emps finally returned to Molech during the Great Crusade, he fortified it so much to protect the portal that he rendered Alivia jobless, so she decided to retire to a quiet life and adopted two children. That is until Horus' little fuckup happened. Horus wanted to use the warp portal to acquire the same powers as his father, and now Alivia had a chance to demonstrate why you shouldn't fuck with the Emperor's friends. Returning to the portal before Horus could reach it, she started a ritual to shut it using her psychic might, much like Emps did on Terra with the Golden Throne, except she did it without a glorified toilet, and in a fraction of the time... almost. Horus arrived just before she could complete the ritual, and because she couldn't divert her attention to fight, she got royally fucked over (as in, impaled with Horus' Talon.), which doesn't really matter because the portal was rendered unusable anyway. At this point she was assumed to be dead, because only the Emperor himself knew who she was, and she disappeared for much of the Heresy.

She was revealed to be alive and headed for Terra on a ship that had escaped Molech, but she had grown tired of trying to cover for the Emperor, so she was just trying to live a normal family life, until one of her adopted daughters got kidnapped by a Slaaneshi cult. Unlike Big E, however, she didn't go on a murderous rampage. Instead, she played things very sneakily, pretending to be a defenseless woman and allowing herself to be captured by the cult in order to learn her daughter's location. Everything was going just as planned, until Severian of the Knights Errant came along and killed most of the cultists in the area, completely fucking up her plan. She shrugged off this minor setback and switched into battle mode, learned her daughter's location by force, and then murdered her way towards the ritual chamber. She interrupted the ritual, saving her daughter and several others, murdered all the cultists in the room and fought off some warp entities. Then she was confronted by a daemonette, which she allowed to possess her before destroying her own body to kill the fiend and regenerating on the spot. If that's not badass, I don't know what is.

Never mind, Graham McNeill ruined the character in Fury of Magnus by killing Malcador via Magnus having a hissy fit and then having Alivia sacrifice her own perpetualness to give it to Malcador, reviving him and killing her. Yes, you read that correctly. Alivia is now dead because the writers needed there to be a twist and decided they haven't fucked up enough characters. If you liked her, fuck you, you are not allowed to have her anymore. Another opinion is that there are too many characters and plot threads within the Horus Heresy to be successfully resolved effectively and Sureka's impactful sacrifice is a better alternative to never seeing the character again.

Also that Alivia Sureka going out this way makes her twice-over the unsung and invisible architect of key parts of the Emperor's vision. She guarded him on Molech, and if she had not resurrected Malcador the Emperor would have never been able to leave the Golden Throne to face Horus. She's by no means a minor character, and she got a much better ending than say, Zephon or Horus Aximand.

Powers

Like the Emperor, Alivia Sureka is a very strong psyker, if we go by the fact that she closed a webway portal faster than the former, and without the aid of ancient technology. However her powers are largely empathic, meaning she can make others like her in order to control them. The downside to this is that she can feel everything her target feels, including pain and death. She is also supposedly proficient in hand to hand combat, but there's not much to go by. Oh, and she's also a perpetual, making her immortal. Unfortunately, Malcador was permanently killed by Magnus' Chaos Sorcery/Psyker Powers (which doesn't bode well for Ollianius Pius and the Emperor in their duel with Horus) forcing her to sacrificed herself to bring Malcador back (Without Malcador sacrificing his immortal life at the Golden Throne the Warp rift and Daemons would have overwhelmed Terra long before the Emperor finds Horus on the Vengeful Spirit. Even if Vulkan blew up Terra the Imperium would have been doomed). The Imperium really is full of martyrs and necessary sacrifices.

Reminder: perpetuals cannot transfer their perpetualness to another person, this has been said many times but it has never said that Perpetuals can trade their life to bring back another Perpetual from permanent death. Though the fact that another Perpetual was sacrificed instead of just a Marine (like what Numeon did with Vulkan) raises some questions on how permanent death and life-trading works on Perpetuals.

John Grammaticus did transfer his Perpetual status to Vulkan, which kept him from decaying when his body died in Unremembered Empire, though. In this case Malcador is noted to be diminished after the fact, much like Vulkan, and it could well be this as much as anything else that explains why he crumbles into ash on the Golden Throne.