Not at all. In fact, going by your definition, it looks like I've run across this before. 
Besides, this is a place for creative works - you don't need anyone's permission to express your ideas. 
"If I had Force powers, vacuum or not my cape/clothes/hair would always be blowing in the Dramatic Wind." - Tenzhi
Characters
Your last RP was a concept that changed with every person that joined it. The more people joined, the more incoherent it became. It diverged wildly from the original path of the thread...
In other words, it was like any other RP Thread, only with slightly less structure.
It had some pretty nifty visuals, though.
My Stories
Look at that. A full-grown woman pulling off pigtails. Her crazy is off the charts.
Think I found a way to have an eternal char AND able to have a full personality range, making a fun little character(s)
Name: Eszter Haledor and Malaise
Age: 16 and unquantifiable
Height: 5'4" and usually 6'8"
Weight: 110lbs. and unquantifiable
Origin: Natural
AT: none and katana/willpower scrapper (has almost nothing to do with rp powers, just defines personality a bit)
Appearance:
Eszter is a normal looking English girl, with pale skin, long blond hair with a slight curl to it, and deep green eyes. She is from a wealthy family and dresses accordingly.
Malaise lacks any strong definable trait in it's true form. When it remains in it's weakest bound form, it may take on the appearance of anything but almost strictly takes on the appearance of a tall and thin yet well toned man. Skin pure white with hair to match, the only striking differences in his appearances being the blood red eyes and blood red embellishments upon his clothes, which tend to be a long white coat, but sometimes takes on a more business suit style.
Personality:
Eszter is a relatively serious girl, she will occasionally smile, but normally seems to have a slightly focused expression. Almost always she appears to have the weight of something great and tormenting looming upon her though she always soldiers on.
When threatened she is quick to get out of harms way, but will fight if she finds it a necessity or entirely to trivial to call upon Malaise t do anything.
Malaise is an oddity. In it's "human" form it almost always has a calm slight smirk, as if it knows something no one else knows. Anyone around him tends to get an odd discomfort, as if they are simply there waiting for something terrible to happen.
To a psychic, Malaise normally appears to be a very shallow/simple being. Very few things cross it's consciousness aside from the usual emotions. Digging deeper into this consciousness however will reveal that it is little more than a shell, almost always focused on keeping something else at bay.
This other consciousness that is imprisoned within is the true one. An eternal being captured within an immortal shell. This entity is entirely enveloped with only one desire, to not simply bring chaos, but to bring a much deeper absolute misery to existence.
History:
Malaise "once" was an eternal being which only existed as what we would know as agony and misery. Malaise was the greater aspect of misery though, a complete and enveloping one that created a hell more terrible than any physical torment or simple mental anguish.
Existence as we know it would be an impossible one if this aspect of misery was still a defining trait. As such, the other aspects of eternity found it a necessity to keeo this misery from ever being an absolute.
Malaise was like any other aspect of eternity, having to be an immortal will that was stripped of all other being but it's most absolute form. Temporally, right as Malaise ascended to become eternal, Malaise became bound. The other eternals had devised an immortal shell that would keep Malaise's true form from uniting with the other eternals.
This form became an oddity, as Malaise was an eternal and as such a defining trait to existence, but wasn't able to unite as a defining trait because of an artificial barrier. Malaise wasn't part of existence either, forcing it to idle forever.
After traveling and experiencing many different universes from beginning to end in many different ways, Malaise eventually began searching for a way to break the barrier that bound it.
It's latest plan was to swear servitude to some beings, over time trickling information to them and insights that would push them towards a chaotic being like itself and eventually transcend. At which point that entity would be able to release Malaise from it's imprisonment.
Malaise bound itself to servitude to the Haledors. As such, Malaise endlessly and with zealot like fervor will protect his project from both the eternals and anything within existence which may harm them.
Ta-Da!....anythin' need some work?
Hey, I love your stuff Monody. I am sad to see your RP go by the wayside too.. nevertheless.. I appreciate your work and maybe, just maybe, I will see your character in one of my threads or one I am in.. keep up the great ideas!
The first negative I see here is the name of your Eternal.
Malaise is already a character in this game. True, he's an ill-defined, background hero character that the devs use whenever they need to throw in somebody with ambiguous loyalties (to this day, nobody is certain as to whether or not Malaise is a Hero or a Rogue because he's been seen in both roles), but he's there.
You might need a different name for that character.
My Stories
Look at that. A full-grown woman pulling off pigtails. Her crazy is off the charts.
Herm...and malaise would of fit him so well. 
Maybe deivos could work. Proto indo european for celestial and conceptual root for demon. >.>
By your friendly neighborhood...uh...iunno...
Any who.
Eternity defined is a persistent and unchanging state external to time and place. Eternity has also taken on a definition similar to immortality, but mostly only because people who don't take phil or something else where you have to know the difference never really bothered to find out and threw the word about willy-nilly.
Point being, the aspects of eternity and immortality that come into play against or with one another.
Eternity is external to defined and finite existence for the most part. As my pondering went before, eternity and eternal entities would be the only thing to have complete and absolute dominion on a level that is truly irrefutable.
Something to note that almost all if not all eternal entities however would likely be "non-entities" without any trace of any kind of subjective consciousness, instead being the absolute defining factors of existence. These non-entities would lack any desire to alter existence purely because there is no point, existence is much too insignificant.
This would not be the only type of eternal entity however. aspects of being could be locked in an eternal state, unchanging and defined only in the sense that they are what existence is. These eternal aspects would likely be somewhat like blueprints in a grand sense.
There is also the oddities in eternality, entities that obtained it almost prematurely in a sense. These would be entities that ascended in a way, but without a proper understanding or frame of mind to grasp what it was that was happening. Instead of becoming greater than even a god, they achieve an eternal state and their consciousness snaps, basically an information overload leading them into a state of being an eternal pile of flabbergasted mush.
Now to immortality. Pretty much anything can be immortal in any of it's iterations. But there's a difference between something like a human being an immortal and something like God being immortal.
Immortal in and of itself is simply to "exist without defined end". In this way a human could be an immortal, but without something like invulnerability they could still die. God however lacks any definable mortal characteristics. What this gives god is the ability to anything and everything fathomable with existence. Technically god could almost act as if it was a true eternal.
The catch, though, is that it is not existence itself. No immortal can measure up to the abilities of an eternal entity, purely because "eternity defines existence". Even God could be removed entirely from history and mind at the whim of a true eternal. The reason I don't define God as an eternal though it has been referenced as one in the bible is because God displays a change of mind and actions, which acts completely contrary to the idea of eternity.
Any who...immortals...
There is actually a conceivable way to have an eternal that acted as an immortal in a sense, but their existence itself is almost enough of a mind twist to rip existence apart. If an aspect of existence was to trap itself, it would be eternally bound as an immortal entity. What this means is that that aspect of existence would cease to be, except for the entity itself. It would also mean that the entity would experience existence even though it technically isn't part of existence. Pretty much everything this kind of entity does would be at direct conflict with eternity and existence. And it's not like eternity can actually do anything about it because it is in actuality an eternal entity that broke it's own logics from everything else.
The simpler immortals would be entities that have somewhat neared ascension. Undeniably far superior to most entities, pretty much the only trait that separates these beings from immortal entities is they have yet to let go of their very loosely bound temporal existence. They still fall very well under the dominion of of eternals, but are the closest existence bound entity that won't rip existence apart.
To RP one of these things would be....well....damn near impossible. You could actually RP the bound eternal, but they would be so overpowered in every conceivable way no one would want you to play one because nothing you do could be denied...If you were a very careful gamer you might play one that has been bound and it's bound aspect seeks to learn more in order to either free itself, or snuff it's eternal side and become part of existence. This is probably the only case where an eternal could be destroyed, but only by itself...in a very odd logic that I really don't want to have to explain...
Would anyone find it objectionable to me engineering up a bound eternal for use in some RP? Think my own RP attempt failed pretty well. :P Mostly I think because I haven't the foggiest in how to manage a forum RP and also because i chose such an abstract concept that it was hell for anyone to really come up with something that actually fit well...