Nashdu: 100(!) min background

Nashdu is a Merfolk Observer, looking a lot like the iconic Skywatcher Adept merfolk.

Full Background:

Found by an expedition in search of artifacts when he was just a baby, abandoned near the Enatu Temple ruins before the first Enatu Golems awakened, Nashdu was taken into custody by a Merfolk Wayfinder known as Raya, who raised him in multiple places. Most of the time in Portage, with the help of the person closest to her, Piqua, one of the leaders of the Tazeem Expeditionary House. Then at times also in her underwater community near Magosi, the Waterveil , or on the go, while participating in expeditions.

"You want to go to Ruins of Ysterid, huh? The sages know they lie at the bottom of deep cave near Magosi Falls. But I don't recommend it. The pit will poison you, boil you, and regurgitate your body up to the surface to be eaten by bloodbeaks."
—Piqua, Tazeem Expeditionary House

Nashdu grew up a very good scout like his adoptive mother, and took an interest in writing expedition logs and reports, becoming the youngest journal-keeper of the Tazeem Expeditionary House. He was always deemed strange though, especially by Raya's merfolk acquaintances in the udnerwater settlement. The elders and sages said there was something strange in his eyes, and treated him as an outcast of sorts, saying he was probably the cursed offspring of a Cosi's Trickster (who are said to be sterile, normally). Raya defended him whenever she could, reassuring him that he was normal, but she changed her mind during an expedition in which he was brought along at the age of 15, which equates to perhaps 8 or 10 in human years.
While exploring an underground ruin connected to a complex of Pit Caves typical of Northern Tazeem, the group ignored young Nashdu's warning and fell into a Cobra Trap, while Nashdu managed to cling to the edge of the pit, grasping it barely with a hand. The snakes actively amassed near the spot below Nashdu, and before the others could act, the young merfolk fell down. The reptiles coiled and jumped with demonic speed, but in a split-second, they all fell dead to the floor, as if hit in mid-air during their assault by some unknown force exactly in the same moment Nashdu screamed after the painful fall. No one could determine the cause of death of the snakes, and Raya began to secretly worry that the merfolk sages were right about the child.
After the expedition, Raya consulted with Piqua far from the ears of Nashdu, trying to come up with a way for the strange mer-child to grow up far from the dangerous superstitions of the isolated merfolk community near Portage. But perhaps also far from her, first and foremost. She made arrangements to accelerate the coming of the merfolk initiation ritual that sanctioned Nashdu as a Free Roamer, and she then suggested him to go to Sea Gate to work as a journal writer there, at the main establishment of Halimar's Expeditionary House, where Raya and Piqua had some acquaintances. Nashdu was happy to embrace that new path he had desired before, the first one as a true independent merfolk, but had also heard the talks of his mother about his strangeness and hid in his heart a deep feeling of inadequacy, which he chose to keep secret.
In Sea Gate, for fear of having his strange nature discovered by the famous adventurers of the House, he worked very little there, just the bare minimum so that Raya's aquaintances could feel like they were doing their job of watching over him, but secretly got involved with a rogue association that aimed at boycotting the Expeditionary House. He was appointed master spy due to his abilities and his favored position in the House, and was in charge of writing and posting around the city pamphlets that exposed the House's dirtiest deeds.He became very close to one of the leaders of the association, a Kabira Evangel with a magnetic charisma and secrets and bonds far dirtier than those of the Expeditionary House. One day, a Nashdu's scoop went a bit too deep and, unknown to him, uncovered facts that were more incriminating for the Association and one of its dangerous clients than for the House. A corp of Enclave Elite  from the Lighthouse was mobilized and began to search the city, in collaboration with the Expeditionary House.
Searching Nashdu's apartment. they didn't discover evidences of Nashdu's secret job, but they casually uncovered a secret diary of the young merfolk, that seemed to contain love letters addressed at a person named only with a nickname. Nashdu feared for the worst when they interrogated him over the matter, and didn't want to answer to any question about it. The Enclave Detectives spared him from the punsihment reserved to citizens uncooperative with the Enclave's investigations, partly due to his young age and partly due to the delicate nature of the uncovered facts, but some details of Nahsdu's writings lead to narrow their efforts and they eventually discovered a link with the Kabira Evangel , and started to uncover everything. Before being caught, the corrupt cleric ordered Nashdu to board the ship of an illegal trader, the client whose businesses were jeopardized by his naive and perhaps too insightful information-reporting which initiated all the scandal. The debt owed by Nashdu to the trader was quantified by the previously friendly cleric to be a stellar amount of gold, and Nashdu willingly agreed to repay it by working for the trader, saving his friend from retortions, if not from the Enclave's law enforcing.
Double-crossed by the "friends" whom he had trusted for their apparent welcoming of his strangeness, Nashdu found himself twice ashamed, with the Enclave and probably the whole Halimar Expeditionary House now aware of another secret he was guarding, one he had hoped could remain so, and that involved his love for the very same person that betrayed him and practically sold him to cover his back.
Nashdu's condition went from bad to worse working for the trader, whose company was far more violent than the rogue Association he had grown accustomed too. He became their Merfolk Observer , sent forward to scout and then organize pirate attacks and sometimes even downright assasinations, most of the times to smuggle relics or just steal treasure, then sold on the black market between Sea Gate and distant Zulaport. Even the shame that Nashdu thought at first to have left behind, followed him to the trader's ship, where he became the most hated and derided member of the crew. He answered to the dark situation by becoming a loner and developing abilities perhaps even darker than those of his criminal comrades, although he always refused to personally hurt any body during the raids, something that only worsened his reputation among the crew, but that perhaps kept his mind from going insane.
His grim conditions changed a bit for the better when a new member came on board, endorsed by a dark and important figure named Indorel, during one of their stops in Zulaport. The man was Vurokk Dahvre, an enigmatic warrior, exotically and fully armored other than always masked (from head to toes), said to have been a Nimana Sell-Sword and a Nighthaze-using Zulaport Runner. He quickly became the second in-command of the ship, right beneath the trader in the chain of command, and despite having become himself the most respected and well-liked member of the crew, he also became the only one to treat Nashdu with respect.
After many a violent raid, and adventures in which Nashdu began to display astonishing abilities, evidently fuelled by the same black mana that powered Vurokk's, one day the trader's ship anchored near an island off the Weastern coast of the Halimar, and the two had a very surprising talk, for the first time eye-to-eye as Vurokk showed his real face to the now adult merfolk. Unexpected drinks followed, and a rushed decision followed the drinks. The rest, as they say, is history... Chapter 1 - Unexpected talks and drinks on the trader's ship.

Nashdu's real nature

The unknown truth is that Nashdu hides in his body a spark of Eldrazi power. This explains a lot of his strange abilities, although there's no easy explanation for its origins. Perhaps the Enatu Temple in which he was probably born from an unknown mother had influenced him with its colorless mana. Perhaps he didn't even had a father, the Eldrazi magic of the site being enough to make a Merfolk woman bear a child of her own. In any case, the following feats and powers are connected to his unique nature. They are listed in order of manifestation in Nashdu's short life:
Ghost Eyes: The feature he had from birth, Nashdu's eyes give off a strange glow under certain lights and he's incredibly good at spotting hidden things and piercing magical glamers.
Foulborn Heritage: The power that manifested when he fell in the Cobra Trap. He's now able to control it, but basically each time he's hurt, he must concentrate in order not to release a destructive psychic wave around him.
Shade Form / Wild Shape + Swarming Locusts: These features are interconnected. Nashdu has two levels of polymorphism, which can also be combined. The first makes him indistinct and blurry and is probably more of a psychic effect like the one above, the second is a completely transformed form that is vaguely animal, but the muted colors and lack of features make it seem "off". In this form, Nashdu can also use the Swarming power, although he rarely does that, because he says it feels awful and because he avoids violent attacks whenever possible. He mainly uses this form combined with the former, becoming practically unnoticeable in the fauna-heavy environments of Zendikar.
He follows Vurokk for months without him ever noticing his presence, even when Nashdu physically protected him from harm multiple times.  
Underdark Climber: After having practiced strange movement modes in his polymorphed states, Nashdu learned an exotic form of climbing that proved very important in the verticalized environments of the Oran Rief, following Vurokk.
Executioner's Noose: This is actually an extension of Nashdu's shadowy psyche, that manifests as a partially-insubstantial tendril similar to those that his quasi-animal forms sometimes display. He uses this attack mainly to hunt and sometimes even just to gather difficult to reach fruits, which he favors over meat in his diet.
Object Projection: Another side of his Noose, this ability has a longer range but can't pull back things, it can be used just to push small objects at blinding speed. He uses this many times to help Vurokk in multiple ways, since the movement is unnoticeable: the transported object "just appears", leaving no clue as to where it came from (that is, Nashdu's hands)
Shadowed Legion: This power is actually an extension of his Shade Form, that manifests as a boon to the hiding skills of everyone nearby. The targets are not required to be aware of Nashdu, so he uses this many times on Vurokk, and he never understood what was going on, something that added to his inane superstitions.
Cloaking Mist: This power is instead an evolution of Swarming Locusts. It always comes from his mouth, but can be used without polymorphing. It's another emergency power that he very rarely uses, preferring his Signature Attack (Fortune Card allowing to re-use an Encounter power by expending a higher level one) that is Provocative Order.
Shadow Soul: An evolution of the synergies between Object Projection, Shade Form, and the psychic power of his Foulborn Heritage, this power bonds Nashdu to a creature and allows him to teleport just as he telelport objects, although it's much more difficult to perform (and thus is a daily power). He can perform a deadly attack combined with this effect, but the effect is not dependent on the attack, so he even used this ability to follow Vurokk closely without having to run for miles like he does (Nashdu's physical endurance is very low)
Dream Partner (Fortune Card): This is one of Nashdu's favorite techniques and it comes directly from his Foulborn Heritage. It basically messes up with a creature's mind, making an attack that was a sure hit, miss Nashdu or even an ally, but weakening Nashdu in the process.
Crab Crawling (Fortune Card): This is connected to Underdark Climber and Nashdu's strange movements while While Shaped. Not easily performed (two cards in a twenty card deck), this maneuver allows Nashdu to crawl with such a speed and grace that it's impossible for an enemy to try to stop him.
Spellplage Surge (Fortune Card): This is an ability that Nashdu can use rarely (two cards in a twenty card deck), and that even when he can, he uses only in desperate cases. It's a physical and channeled manifestation of the psychic wave generated by his Foulborn Heritage, disconnected from the pain reaction and coalesced into strange colorless fire, not very different from the one used by Ugin right at the Eye of Ugin. The fire comes off at first as an innocuous explosion and encircles everyone in a large area, friend or foe, without causing damage. The affected creatures are then able to use it with each attack, for a short time. Nashdu used it to empower Vurokk's attacks one or two times, again feeding Vurokk's wild superstitions.