In the 41st millenium there is only......continuity errors?

[Midnight Ethereal]

I've been recently confronted with a problem within my fictions and short stories. The problem deals mainly with the fluff of the 40K universe, I'm only moderatly versed in the ancinet scrolls and icons of the Imperium and and the Emperor's territories, but I'm seemingly needing more information; for starters:

I recently was going to enter a short story of mine for the Fiction contest, this short story was about a custom made chapter of Space Marines known as the War Lions, my only problem was at the time I hadn't known that much on marines, only that they carried bolters, wore power armor, used gene-seeds, served the emperor, etc. Still When choosing a Chapter planet I was compelled to make my own planet, thus I developed the savannah world Lonais.
However the problem with this is that I was never truely sure if I could do such a thing and because of this I strayed from my Short story of the War Lions and their desperate battles against Hive Fleet Basalisk, also custom made. So my question is, can planets be "made up" for the purpose of Roleplay and fiction, or is this highly frowned upon and will it it result in my excommunication and probable execution, via the Inquisition.

Mainly this question goes to the creation of planets and chapters, for I believe I need the War Lions to be a sucessor chapter. Either way The reason I ask this is because after reading some stuff out of codices and novels I realized that new planets would be rare, I think. Considering Tyranids are invading from the east and the south of the galaxy and other than that I'm not sure about the west and the north.

If this topic doesn't get locked, and hopefully I put it in the right place, Ill probably add onto this with more questions, but I think this is a good source and possibly a potential resource to others, correct me if I'm wrong and please don't burn me with a flamer.  

[Jinalee]

I believe making up planets is OK. I myself have done that, calling a starsystem Turis (From the word "Tourist" razz ), and I have made it specifically for a custom Space Marines Chapter, named Brightstar.

The rulebook states, that there are roughly a thousand (1.000) Space Marines chapters, and over a million planets. So there is almost unlimited possibilities. Also over Eldar Craftworlds, Dark Eldar Kabals, Ork Waaghs, Imperial Guard Regiments, Tyranid Hive Fleets and Tau Septs. Even more races are allowed, that, the rulebook says as well. Somewhere.

Oh, and Brightstar are a Succesor Chapter from the Crimson Fists. Em... Yeah, that's about it. Nevermind. And the ony fluff I know of Space Marines is the stuff you know as well, so I'm pretty. Blank. As you call it in Danish/Faroese.  

[Glorious Leader Luna]

rule of thumb if you want to keep it Canon-like only make stuff what does not effect the canon massively or even better not a all

thus Space Marines chapters are ok there are far more than the Imperial can keep up with as are planets

Hive fleets on the other hand are a no no  

[Jinalee]

Hive Fleets are a no-no? How come? Well.. OK, I think I can see what you mean... I think.  

[Vikki Stardust]

You can do whatever you want, as long you don't break the base rules. (or turn marines into stinking furries yuck!) Why are Tyranids no-no? Have all splinter fleets been erased from the background as well now?  

[Caleidah]

Only the massive Hive Fleets are no-nos, as their size/scale is something that would be very, VERY closely watched. Splinter fleets, being smaller, are easier to use without snapping cannon in half.  

[Midnight Ethereal]

So in the event that a splinter fleet were to begin plauging imperial worlds then how big of a force would intercept them. Considering the threat of tyranids I had considered the possiblities of maybe inlisting the Adeptus Mechanicus and a titan legion (or more) other than that I had three full chapters doing combat with this fleet.
So yeah I still need to edit this and then once I work out all my kinks I'll probably submit it or something along those lines.  

[Jason Kharo]

Meh, I'd say 3000 Space Marines is abit much, maybe even 500 could deal with a Splinter Fleet, and another thing, I wouldn't enlist a whole titan legion, thats a lot of titans, maybe just two Warhounds, three Reavers and maybe a Warlord or possibly a Emperor.
Last thing....

DEATHWATCH
You neeeeed them, really, they just kick a**.  

[Azrael Swift Blade]

Hive fleets are not a no no, they are a yes yes. If you've been playing the game for a good time you'll know that people will make up their own splinter fleets and in time you can create a hive fleet, in fact the writers of the Tyranid codexes will emplore you to create your own. The universe of Warhammer 40K is so vast that you can create anything to do with Tyranids or even Space Marine chapters and planets.