Vulkan

"'I have returned to bring peace and friendship throughout the Imperium, no matter what the voices in my head say!'"Vulkan is the Primarch of the Salamanders, and eighteenth son of the Emperor. Vulkan is unique among his brothers in that he is a Perpetual, meaning that he is effectively immortal, as his body will simply regenerate after death.

Official Canon
Vulkan was found on Nocturne, where he had formed a strong bond with its people, and taught them mastery over forgecraft. Vulkan was reunited with his legion, the Salamanders, who specialize in master-crafted gear and flame weaponry. Known for his great humanitarianism, Vulkan openly banned the use of Phosphex, rad-weapons, and other terror weaponry in his legion during the Great Crusade. He also got along well with most of his brothers,

Horus Heresy
During the Horus Heresy, Vulkan was among the first wave of loyalists sent to bring Horus and his traitors to Imperial Justice. However, he, Corvus Corax, and Ferrus Manus were betrayed by their brothers Lorgar, Konrad Curze, Perturabo, and Alpharius Omegon, in a battle that would be called the Drop Site Massacre. While the loyalists survived, they suffered heavy losses, including the primarch Ferrus Manus. Vulkan died as well, but being a perpetual, his body recovered, but was captured by the traitors.

Vulkan was given over to Konrad Curze, who used Vulkan's immortality to his disadvantage as he slowly tortured him into insanity. Vulkan eventually escaped and reunited with the loyalists on Macragge, but was too far gone to be of much use until he was stabbed by a mystical weapon that restored his sanity.

Post-Heresy
Vulkan had been among those who opposed Roboute Guilliman's Codex Astartes; as his legion had been decimated, he had barely any soldiers left, and was opposed to the idea of breaking up the legions. During the War of the Beast two millenia later, Vulkan was the last primarch known to still be operating in the Imperium, having personally dueled one of the massive Ork Warbosses known collectively as The Beast. He was only able to defeat the Ork just barely; he pushed the Beast into a generator full of WAAAGH energy and was exposed to the blast, killing him.

Since then, Vulkan has disappeared entirely. According to the salamanders, he will return if they find all nine artifacts of Vulkan, and so far they have found half of them.

TTS Canon
Magnus the Red claimed that Konrad Kurze had tried "very hard" to kill Vulkan "with a fork."

Reapperance
The Emperor orders the Ultramarines to find the remaining artifacts so that Vulkan will return, to which they succeed in a very short amount of time. Vulkan immediately appears via drop-pod to congratulate the Salamanders, though he reveals that he is still insane as he is haunted by the ghost of Ferrus Manus. He is very enthusiastic about friendships.

When Magnus and Kitten attempted to steal the Engine of Woes, Vulkan revealed that he was still alive (and more insane than he had been) because he had absorbed some of The Beast's WAAAGH energy, and reformed at an unknown time with some Orkish tendencies. Magnus later relayed this information to the Emperor, expressing serious concern that part of the Ork gestalt had fused with his mind. The Emperor complained that, now that he had one son who was half demon, and another who was half Ork, it was a horrid way to get an extended family.

Despite Magnus' treason, Vulkan wanted eagerly to hug Magnus in spite of his protests; Due to a spinal injury, Magnus freaked out and accidentally killed Vulkan by throwing the Engine of Woes at him, but he was revived five minutes later, and swore to follow Magnus (and tour the Imperium at the same time) alongside his recently found brother Corvus Corax.

Catachan Capers
While very eager to be reunited with his father, Vulkan was insistent that he and his brother should aid the Catachan Jungle Fighters, especially since they could use the reinforcements during their crusade. Corvus was surprised by Vulkan still being able to still make logical decisions, but he was quickly disappointed by Vulkan getting himself killed (again) when he wanted to pet a Catachan Barking Toad.

Attilan Assault
Vulkan died a third time when he and his brother were aboard the Marbo's Glutes, which was crashed by the traitor Clancy. Vulkan quickly recovered (somehow still being able to talk while his head was just a skull) and interrogated Clancy; Vulkan ordered to keep him alive until they could discover who Clancy's allies were. Vulkan was able to tame some Ovigors by hugging them, allowing the survivors to quickly travel to Khanasan.

There, Vulkan was told that the only astropath that could warn the fleet of the impending exterminatus was Starass, who would've been unable to communicate with the fleet, being an ass. Vulkan, enraged by Clancy's inability to understand true friendship, hugged Starass to deliver the message to fleet. However, the message came too late, and the missile had already been launched. Vulkan and two Attillan volunteers flew a gunship into the missile, with Vulkan leaping out to hug the missile, dying a fourth time. Vulkan crashed back to the planet in a smouldering ruin.

Jopallian Japes
While Vulkan recovered from his most recent death, it became apparent that his system had been infected by the Life-Eater virus. Clancy had previously used Corvus' memento virus bomb in the failed exterminatus attempt, and the virus that was now in Vulkan's body was killing him faster than he could regenerate. While Corvus, Tu'Shan and He'Stan sought medical supplies and construction equipment on Jopall to cure Vulkan's affliction, Vulkan himself was bedridden and slowly wasting away. He did, however, continue to be supportive to his sons Tu'Shan and He'Stan and their efforts to save him; even as they buried him under artisinal death-masks of his own face.

Ultimately, despite the Salamander's best efforts, and Corvus leading a revolution on Jopall, Vulkan would die from the virus before he could receive medical attention. Unexpectedly, however, Vulkan would reawaken in his Ork persona and seemingly use Waaagh energy to cure himself before vanishing, all whilst claiming that while it was fatal for a man the virus 'wasn't hurty' to an Ork.

Vulkan's TTS Deaths

 * Crushed by the Engine of Woes when Magnus threw it at him
 * Poisoned by an exploding Catachan Barking Toad after petting it
 * Burned in orbit/upon impact after Clancy crashed the ship
 * Hugged an Exterminatus missile
 * Residual infection of Life-Eater Virus from the Exterminatus Missile

Quotes

 * "Father's remains must too be embraced, they do, ONE BRITTLE BONE AT A TIME!"
 * "I want to boop the snoot!"
 * "Sorry friends, the corner of the room is very dark for some reason! I tend to use it for them dramatical entrances in case someone tries to GRAB ME FLASHY BITZ!"
 * "How long's it been Magnus? Ya know, since you did that whole betrayal thing? Remember that? DAT WAS CERTAINLY A FING YOU DIDZ, ROIT?!"
 * "Why am I alive? Why would I want to be dead? Being alive is FUN! All my FRIENDS are here! Besides, I tried being dead - UNPLEASANT IT WAS!"
 * "That day, pain and I became the BEST OF FRIENDS!"
 * "I but want to give my brother a great big 'I'm totally not mad that you ruined everything forever' hug!"