How can I prevent my homebrew space marine chapter from being mary sues and generic

Make them as wide as two space marines, but just as tall, to make doorways difficult

What do you have so far for your chapter lore anyhow, OP.

if you truly want them to be space bretonnians then their founder has to be an eldar waifu

Make 'em be self aware and non-serious ;o3

>their founder was an eldar waifu

i think you meant the founder waifued an eldar

unless you typed exactly what you meant

in which case, that opens a whole nother can o worms right there

>doesn’t use imperial guardsmen like disposable peasant levies
0/10 do you even Bretonnia?

>dark angels successor chapter >colour scheme is more ''heavenly'' than other succesors because their relationship with the unforgiven is strained >over religious like the black templars >all of the companies use ravenwing vehicles and tactics >had chapter civil war after they found out they are of dark angels descent >they treat the non astartes citizens as slaves unless they are rich or completely follow the imperial cult >their homeworld during the age of strife used to have a cult dedicated to a dead eldar goddess but when the ecclesiarchy arrived they portrayed her as a saint who saved the planet instead of a goddess >the IG regiment of their planet is overzealous just like them and are called shield martyrs and the chapter says it is a ''great honor'' to be a cannon fodder and they only recruit the gullible ones I'm going to continue this

sorry if the writing is bad because I'm writing this in a phone

>caring about fluff.

Just play the fucking game.

Have them do particularly well against one race at best. MAYBE two, and only if there is a logical reason for it. Make sure to have them get fucked by this race once or twice when that race did something unexpected. Just because your chapter usually has the Tyranid's number doesn't mean they were expecting the Flying Circus, for example.
Have them make administrative fuckups. Occasional bouts of administrative incompetence is potent.
Have them insist on something stupid. Space Wolves have wolves everywhere. White Scars send people on petty revenge missions. Reasonable Marines are Sue Marines.
Don't make your chapter understrength, or lacking equipment, or some other underdog bullshit unless you are prepared to reiterate that they get their shit kicked in for this deficiency. If the great Chaplain Tantrum left the chapter with nary a landspeeder to their name, this needs to come up, not just be an excuse for you to not field a unit you don't like anyways.

Make them hail from a feudal world, where being a Sapce Marine is the pinnacle of achievment for young nobles. They train and duel constantly in the hopes of being chosen by as Neophytes.
They are very heroic and honor driven, but see non-nobles as garbage.
They still plot for their families, so expect a lot of squabbles despite being true brothers in arms. Personal heraldy on the armor is a given.
Basically the three musketeers in Space.

The distaste of Brets for ranged weapons will be harder to replicate, unless they use a lot of servitors and serf-crewed vehicles.
Also the french love grenades like you wouldn't believa, and afaik there's no SM chapter with a fixation on explosives, so that might be a nice angle.

the star phantoms already fill that niche, tho.

since brets are chivalric, my chapter uses mostly uses ravenwing tactics and vehicles since the 2nd company uses bikes and other fast vehicles

An entire chapter of related.
I dig it.

>how can I prevent my homebrew space marine chapter from being mary sues
Give them a flaw.
>generic
FInd some way to make them visually distinctive. Whether through kit-bashing or some third party bits, find some way to ensure that every unit of yours standouts somehow from the stock GW version.

during their civil war, their grand master chaplain summoned strange daemons of an unknown chaos god and that he wants the chapter to destroy itself as a sacrifice to the god and bring order and the destruction of free will in the galaxy

Bikers of all stripes, and then assault units for everything else. Meltas are permissible for range+AT purposes, since it's a 'lance' of pure light. Heavy support can otherwise be handled by an allied Guard detachment Or if you want to go hard-mode/extra chivalrous, Sisters

Marines that work well with IG/Sisters are Reasonable though.

They are a loyalist chapter composed of Beastmen, trying to find more member for their holy crusade. They wander the galaxy in search of new recruits and when they are strong enough they start a suicide camping against a chaos infested world in order to redeem themselves in the eyes of the Emperor.

Dragoon SM, with no rhinos but where infantry moves in bikes and disembarks prior to battle, alongside regular cavalry, would be cool.

I suppose flamers would be ok too, since they aren't firearms per se.
Why not use melta-tipped lances, tho?

Bret knights are very pious, this could work.
And we don't have a lot of chapters working with the Ecclesiarchy.

Melta lances are possible, just don't see them particularly often. Time to put that x-acto knife and greenstuff to use!

As for flamers, I think it could go either way. On the one hand, burning people for heresy/crimes would've been a very medieval way of handling things. On the other hand, it's not a particularly chivalrous or honorable weapon. Maybe they can be utilized against xenos/heretics rather than 'proper' foes.

Knights are another ally option, if a bit blunt

St Celestine has a flamethrower sword, and some supplement in dark heresy had flaming powerswords. Just say they're rare archeotech or something like that.
Flamethrowers might be seen as honorable, too. They may even have developed ritualized duels with flamethrowers.
As long as you use shields and armor, it might even be less dangerous that regular blades.

About knights... I think it won't go well with nobles space marines to have a bigger kid in the block. It's hard to be uppity when you fight alongside people with a pedigree fighting inside giant robots.

do powerspears or chainspears exist

...

1d4chan.org/wiki/Space_Marine_Chapter_Creation_Tables

Wanna roll to finish fluffing it out, OP?

i dont have a dice but i'll try a dice rolling simulator

Rolled 6 (1d10)

there's anydice on the web, or you can type
dice+1dX
in the option field.

I dig the idea of assholish, holier-than-you marines full of furia francese and rigid guidelines pleases me.

What if the veterans use only blades because of "muh honor" and traditions, and the boots are forced to use bolters until they've proven their worth?