@JbcoolIn order:
My original point was that a psykers abilities are limited less by the psyker himself, and more by the amount of warp energy on hand. If I was mistaken about the amount of latent warp energy present, then that's my bad. That said, there is still a greater amount than normal on hand, so a psyker would be far from hard-pressed to go throwing powers around.
Quoting Warhammer 40,000 Wikia, page
Immaterium; Emphasis mine:
"The Immaterium (also referred to as the Empyrean, the Aether, the Sea of Souls, the Realm of Chaos, Warpspace or most commonly, the Warp) is an alternate dimension of purely psychic energy that echoes and underlies the familiar four dimensions of the material universe. It is the
source of all psychic powers and known instances of so-called "sorcery" or "magic" as well as the home dimension of the Chaos Gods and their myriad daemonic servants"
Strictly speaking, warp energy and what can be done with it is a bit better explained in 40k than in most settings. However, it still operates on the same basic lines of logic and reasoning as magic generally does. It has little to no actual rules, it's random by nature, and as a source of power it's shaped not by any inherent laws of nature, but by the sheer willpower of the one using it.
Orks are odd, in terms of psykers. Yes, they need to learn to control it, but gathering and expelling energy, and great deals of it at that, is how weirdboyz work in general. Any weirdboy, regardless of his skill or general power level, would easily be able to murder three of four tactical marines in a single blast of power, only to do it again a minute or two later. Skill only determines how likely they are to die when gathering the energy they need to do it. What's important to note here is that
Waaagh energy is still psychic energy, and thus
warp energy. The only thing that makes it special is that it exists in the matterium because orks constantly radiate it like heat from an open fire. This also means that normal weirdboyz are all but immune to the influence of chaos. Urgrugg isn't, but he's special.
Naturally, ork weirdboyz are more than capable of competing with librarian and sorcerer level psykers, at least in terms of damage output. How they work is straightforward. When around other ork, they absorb the latent psychic energy of the Waaagh field that all ork emit. In fact, they tend to absorb so much that if the Don't unload it, they'll explode, or die in some other horrible manner. This energy is so powerful, it allows them to spew gouts of warp-plasma from their mouths that will reduce lightly armored tanks to molten slag. Throwing out massive blasts of damage is just how ork psykers work, in general.
In terms of skill, Urgrugg is what is known among orks as a warphead. This means that he has learned how to regularly gather, manipulate, and wield Waaagh energy. When he was young, and still living with his tribe, he spent about forty years doing this, all while regularly participating in combat. For that to be true, and him to have lived so long, he would Have to be at this level of skill. Otherwise, he would have killed himself within a year or two just trying to handle all the Waaagh energy that is naturally produced in massive sums on an ork battle field.
What makes Urgrugg unique among weirdboyz are two things:
1.) He's able to draw power directly from the warp, and not just the warp energy that makes up the Waaagh field. The reason he can do this is what I've been keeping secret. It all ties back to his home world, and even further back to the creation of the orks as a race. Originally, the ork race were called Krork, and were created by the Smart Boyz (know to everyone else as the Old Ones) to defeat the Necrons during the War in Heaven. However, when the Old Ones were defeated, and the Necrons retired to their tombs to wait out the death of all other things in the materium, the Krork were still alive. In some cases, like that of Urgrugg'ss tribe, the death of the Smart Boyz left them stranded on an isolated planet.
Keeping in mind that they were created by the Old Ones, who were able to bend reality to their will like gods because of their sheer mastery of the Immaterium, and who also created the Eldar, I thought it wouldn't be a stretch to think that the psykers of their warrior race would be able to draw power from the warp. The ability to be powered by the presence of other warriors seemed like a logical solution to fighting the necron null-fields that cut off areas of space from the warp entirely.
The idea of Urgrugg is that he was born as one of these psykers, a remnant of the latent potential that resides locked in the DNA of all orks, but has been selectively culled out of them over the millions of years since their creation.
2.) Naturally, as there basically aren't other psykers like him among orks, he had to learn how to master his non-Waaagh powers some other way. This is where his dealings with daemons comes in. In exchange for teaching him to control his powers, giving him access to a much wider variety of abilities than the average weirdboy, he promised them his body and soul as a prize when he died. Wanting the secrets of the Old Ones, the daemons excepted. As a trick, though, they inscribed runes of power into him that mutated him, and cut him off from the Waaagh. This forced him to rely even more on the daemons, which led to further mutation and insanity which is generally common among normal psykers. Being trained by daemons, specifically those of the ranks of Tzeentch, he naturally is a very well-trained psyker.
All that amounts to the basic concept behind how Urgrugg exists, mostly because I couldn't think up anything less elaborate that would allow a weirdboy to have powers without an army of ork around him.
At the end of the day, it's hard to pinpoint where Urgrugg stands on the Imperial Assignment chart. Being an ork, he'd probably be classified as an Iota-Eta level. However, when you compare known and frequently used weirdboy powers to what librarians are able to do, at least in terms of destructive combat powers, he's fully capable of competing with shadowseers and librarians. All weirdboyz are. That would put him somewhere around Epsilon-Zeta level, possibly higher. However, as I've said, when it comes to small, subtle things, he's basically useless. Where a normal Iota level sanctioned psyker could easily manipulate a pen to write his name with ease, Urgrugg would probably blow up the table trying. That's why everything he's done so far has only been large-scale.
I'm sorry that people are feeling upset for Urgrugg's power level. Unfortunately, that's just the standard M.O. for ork psykers. They're not like humans, and the rules for how they work are completely different. From day one, they begin immersed in power that they are forced to expel violently through acts of devastating destruction. Unlike humans, they also don't need training to learn to control those massive sums of power. They were literally purpose-built to do just that. If he didn't know how to control it, then as a battle-hardened ork Urgrugg would be dead by now. So, he has to know how.
That said, my intent was never to harm the other players. My plan was to have some genestealers show up, then to make a show of blasting them and not the marines. You know, as a show of good faith.