OddJars

Alright, legions and chapters are different. Legions were infinite marched with their primarchs, and had direct control over all support vessels (space travel). After the heresy the remaining loyal legions broke down into chapters (except the space wolves). Each chapter traces their lineage back to a primarch but established their own history from there forward. A chapter has a "fighting strength" of 1000 battle brothers. Some chapters are bigger or smaller but the bigger ones have to be wary of the inquisition... Chapters also have limited space vessel presence to theoretically keep them controllable and prevent another heresy scale event.

 

I'd recommend creating a chapter from a later founding. Foundings have happened a few times in the history of the game and they are left purposely vague and full of holes. Many later founding chapters don't even know their primarch. This could totally allow you some leeway. I'd say read up on all the primarchs and pick one that embodies the type of warfare you like, then decide weather your dudes take pride in that connection, despise it, or hide it in order to further their own interests. Don't tie your stories in with too many of the big players except in the loosest fashion to avoid "getting corrected" as the black library keeps putting out books.

 

Simple tweaks to your above story could easily have them being part of the emperor's children who stayed loyal aligned with a loyal legion then split into their own chapter during the original founding. Current fluff names most but not all the chapters created at that time so you can be as old as you want. There was even a cursed founding, 13 if memory serves. These guys tended to mutations and unexplainable mental issues.

 

My personal chapter is the dark star saviors. They draw their lineage back to Peterabo (spelling), the iron warriors, however they were a large garrison out on the fringes that passed themselves off as a loyal chapter once they were rediscovered. They have no love for the emperor nor chaos and I use imperial fist rules for them as this gives me the siege warfare feel I want. I play an aggressive give no quarter expect none style. I revel in making my own stories and leaving heresy time in the far history that my chapter just doesn't worry about.

Ah, I see, then maybe instead of the whole lost primearch thing they are instead a chapter with a history that no one knows except for them and they disappeared during the Heresy and suddenly emerged during the 40th millennium. They have a deep hate for Fulgrim and Slannesh because they were almost completely destroyed by the Emperor's Children during the Heresy. They only recruit from rich planets, mainly from Cupidius (my made up planet) because of their hate for the poor. No one knows why they hate the poor so much but it may link back to their homeworld. They are also very curious people and secretly make deals with Xenos and Chaotic forces and have a big collection of forbidden Artifacts in their secret museum. Their current Chapter Master is Percival Ravenaught, a very silent man with a surprising sense of humor because he make the dumbest jokes when you least expect it. They also have a weird way of thinking and absorb information at an inhuman rate, this is mainly why their thirst for knowledge is so strong. They are also nocturnal and preform exceptionally better during the day. Their tactics are aggressive and fast and love to use loud noises to alarm their enemies and cause massive damage then run away, leaving their opponents in a crippled and confused state. Their colors are mainly Gold, Brown, and White and their weapons are painted a bright gold. The gold also helps them since it blind their opponents during their hit and runs giving them more advantages over their enemies. Their logo is a wing of an owl with a gold eye in the middle. What I am going with when it comes to this chapter is a group that are rich douchebags that are morbidly curious and open to allying with Xenos and they hate Slannesh. Their battle cry is "Our toe is worth more than your pathetic lives!"   

One tiny bit of cannon fluff states that the space wolves actually purged the two missing legions prior to the heresy. The primarchs mention their missing brothers and how the wolves may be unleashed again...

 

How bad must those two have been to be removed from history when not even the chaos ones were? Personal note, I think not so bad as after the heresy the emperor wasn't conscious enough to expunge further records...

 

Cool bit of fluff beyond that tho.

Here's what I've got so far for my custom Chapter the Storm Owls.

Basically before everything went to [big bad swear word] because of [big bad swear word]ING HORUS they were known as the Void Owls. Their homeworld is Cupidias where most of the population were nobles and scholars.They loved knowlage and loved to learn about almost anything and they were complete assholes and looked down upon the poor. To show their status they wore bright gold and even painted their weapons gold. But during Horus' rebellion Fugrim and the Emperor's Children assassinated their Primarch Sebastian Miles(One of the lost primarchs that I made up) when he didn't join his brother during the heresy. This started their deep hate for Slannesh. After this event they were in despair, their tactics became more ferocious. Their name then changed to the Storm Owls because of their use of loud, earsplitting, weaponry(not sound cannons because [big bad swear word] slannesh,not literally oh god) and their fast hit and run tactics. Of course over the years their curiosity grew. They started allying with xeno races and even some chaos forces in secret and started a collection of xeno and chaos artifacts that they hide from the Imperium. They are still douchebags though. I want the 40k community's opinion on this. Thanks!

Cool! Thanks for the info!

Just a quick question. Are homemade chapters possible in 40k. I'm pretty new to the hobby but I'm planning on buying the Space Marine Codex and making my own custom chapter since I enjoy creating custom stories and factions to immerse myself into the lore of a universe more but I'm not sure if people dislike playing against players who use custom made armies. I still plan to follow the rules of the Space Marines though I just don't want to use a chapter that is already in the official lore.                         

Are you guys open on weekends? I really want to play 40k but I cant go during the week.

Quick question, can I get by alright by just using the base paints? I don't want to spend like $120 extra dollars if the miniatures look fine without all that extra stuff. 

Thanks for the replies guys! You guys are helping me a lot! I have to say, the Warhammer 40k community is probably one of the more noob friendly communities out there. 

I bought the Dark Vengeance Pack not to long ago and I need some help from experienced players. First, what kind of things should I avoid doing in combat and what are some basic strategies and play styles for the Dark Angels? Basically, how do I not be a noob. Next, what is the best way to save money when buying new units and paint for my army (I want to get at least 1000 points into my dark angels) and what kind of modifications can I make to improve the army that the box came with and what units can I buy to improve that army so it can be viable and maybe even good in competitive matches. Also where are some good places to play around the West Linn area and are other players willing to take some time to help a noob out, from what I've experienced from this community people are pretty willing to help out new players, but that can just be a small amount of players who are like that? Finally if it helps, generally in rts games I like to cripple the enemy early on so I have an advantage from the beginning, I also like to play aggressively and I want to incorporate that play style somehow into this game.