Sigil

 All living things absorb magic as they grow, stored in the carbon that makes their bodies up. As they grow, and die, they pass down through the soil and becoming oil and other carbon deposits, these deposits continue to absorb magical energy, slowly turning into Sigil.

Sigil is the lifeblood of new world, magic empowered crude oil and coal which drives steam/dieselpunk mecha called Derricks: steam powered multi-legged arachnomotives, Iron Horses, dieselpunk wargear armour called Sidearms, etc. In order to "suit up" into the armour you need skin to metal contact through a special oil medium, and only women can use the armour, so there's lots of scenes of western cowgirls in underware/bikinis rubbing each other down with oil and squeezing into tight-fitting mecha suits.

The heart of the story, though, is a family's tale of vengeance painted against that backdrop as two sisters fight a greedy, evil land baroness to regain the rights of the land their mother, a Texas Ranger, died trying to protect.

Art direction will be handled by Satoshi Urushihara. Because who better to handle glossy, oiled up lesbians squeezing into mecha suits... except maybe Shirow.

1. Back East
The Colt Sisters, currently attending university in Boston, return to their dorm room to find someone waiting for them: a slimy seeming lawyer who tells them that their mother is dead, and all they need to do is sign off on selling off their mother's assets to get a hefty sum of money.  Distraught and suspicious, they throw him out of their room and try to find out what is happening.  They receive a telegram from one of their mom's oldest friends, a bounty hunter, who they decided to meet up with to find out what's happening.

2. Iron Horse
On the trainride back to their old hometown, they sisters find themselves under attack from bandits who seem to be more interested in capturing the pair than pilfering the train.  Quick thinking and determination let them give their foes the slip for a while, but the pair are eventually cornered, but are saved at the last minute by Olympia Mossburg, their mother's friend, who was afraid something like this would happen.  They turn the bandits over to the sheriff of a passing town and settle down in their cabin to talk.

3. Bad Blood
Mossburg details the last year or so of their mother's life through flashbacks, explaining that she was in contention with Michelle LeMat, a local rail baroness who had been buying up all the land in the area for inflated prices, and using intimidation and threats for force those who didn't want to sell out to do so.  Sheriff Colt was one of the largest landowners of the area, having a particularly large ranch and mine complex, and had rebuked multiple attempts to sell her family's home.  Mossburg wasn't sure exactly what had happened on the night she died, but the girl's mother had broken her promise and gone to confront LeMat alone.  LeMat had an alibi for the entire evening and denies ever seeing the sheriff, so there's no proof of who actually killed her.  However, the sheriff's will specifically left all the lands to her daughters, who now have to figure out how they want to deal with their mother's death.

4. Homestead 1
The girls return to what was once their home growing up to find it mostly deserted now, a symptom of LeMat's buyout.  They also find LeMat herself waiting at the train station for them, and wanting to speak with them.  She talks with them about why she wanted the lands (to rebuild the dying town, restoring it with an influx of new money once she brings the railroad through) and she continues to refuse to have anything to do with their mother's death. She seems genuinely sympathetic towards the girls.  The girls go home to talk over what it is they want to do now, promising to talk with LeMat again in the next few days.   Mossburg tells them she'll support whatever decision they make, but that whatever they do, not to to trust LeMat.  The sisters agree to look into LeMat's claims.  The sister's spend some time around town, talking to people, and discover that the whole town is overrun with bandits and hooligans who damage property, threaten people, and cause havoc.  Without the Sheriff to hold them back, they're becoming increasingly brazen.

5. Homestead 2
The sisters wind up helping the owner of the local store deal with a dangerous looking ruffian, and they discover that LeMat's buyout values have dropped since the sheriff died.  She's barely offering a quarter of what the land's worth now, much less what it will be worth when the railroad comes through, seemingly because she knows that no matter what, the holdouts won't be able to refuse to sell if the town gets much worse.  They travel across their own property to check for problems, eventually ending up at their mother's old silver mine, now abandoned.  It never made money, being a small vein of silver, and was more a hobby than anything else.  The sister's follow a couple of hoodlums inside, only to be tricked and sent plummeting down a shaft elevator to the bottom, followed by a few sticks of dynamite.  As the smoke clears, the two sisters can hear the hoodlums above telling them this was all courtesy of Miss LeMat, to teach them not to stick their noses in where it didn't belong.

6. Getting the Shaft
The sisters begin working their way deeper into the shaft, away from the cave in, in the hopes of finding an exit somewhere further down the line, and talking about what to do about LeMat.  Eventually, the two discover a small alcove where they used to play as kids, digging and panning silver, and how their mom always promised to turn that silver into "stars just like hers" when they grew up.  Seeing a familiar marking, one the knew their mom used to show them safe paths through the mine inscribed onto a flat wall, they pushed through a secret door to find a new shaft dug deeper into the mountain.  As they pass through, they begin to see the walls streaked with, not silver, but arcana-coal.  At the back of the mountain they find a workshop where their mother was apparently working on improvements to her gear, including the maintenance area for a Derrick and Sidearm, each bearing a gunbelt adorned with a pure silver sheriff's star.  Here they find their mother's diary, which reveals she discovered the real reason that LeMat wants the land: it's covering a previously undiscovered cache of Sigil fuels. She wants the undisputed mining rights to the area, and is only bringing the railroad in to facilitate distribution once she has the mining and drilling rights in place.  With the help of their mother's improved law enforcement derrick and sidearm, they two clear the rubble and escape the mine, swearing that they'll take up their mother's path, becoming sheriffs and proving LeMat's criminal escapades.

7. Circle the Wagons
LeMat's second meeting with the Colt sisters goes considerably different, and the two swear to do everything in their power to not only stop her, but to reveal her plans.  Her demeanour changes instantly, and her parting shot as she leaves is that "she hopes the two girls won't live to regret their choice".  It's mere hours later that a particularly large group of outlaws burst into town, and start roughing up the few remaining townsfolk.  It's up to the sisters to once again don their wargear and turn the tide against the force invading the town.  Mossberg makes a return appearance, and despite the older sister being injured, the three manage to turn back the outlaw brigade after a particularly tough battle.

8. Sawbones
While a doctor friend of Mossburg and the girls' mom helps treat the older sister's injury, the younger takes to practicing with her Derrick, blaming herself and her lack of skill for her sister's injuries.  The older sister, in a fever-dream induced by the injuries she suffered, recalls how her younger sister always tagged along with her growing up, and how she always regretted letting her get hurt one particular time when they were younger.  The two, despite being separate, are still united by their desire to protect one another and the town.  The episode ends with the two agreeing that, no matter what it takes, they won't let LeMat win.

9. Mystery House
The girls, having gotten used to their duties as sheriff and patrolling the town, go to turn in for the night only to discover a ghostly figure drifting around.  The sisters follow the ghost, which they first assume to be their mother.  The figure chastises them for being reckless and dangerous, for putting their lives on the line without thinking about the consequences.  The sisters soon suspect this spirit isn't who she seems to be, and eventually reveal her to be a fraud.  While normal weapons don't seem to do her any harm, they eventually discover that burning Sigil Oil will repel her, and defeat her.  The episode ends with LeMat blaming the failure on her subordinate, a sallow-skinned victorian dressed woman named Winchester, who summoned the spirit, and telling her that such parlor tricks are no substitute for flesh and blood action.

10. Broken Arrow
The sister's arrange talks with a local tribe of Native Alv(elves) with the hopes of, if not enlisting their help against LeMat's plans, then at least showing them the bad she is intending to do.  They end up running into one of LeMat's subordinates who is there delivering "gifts" to the tribe.  The Colt Sisters and LeMat's crew eventually end up getting into a fight, damaging many of the tribe's homes.  The Chieftaness chastises both the Colts and LeMats men for their actions.  LeMat's forces leave, and while the Colt sisters try to explain themselves, they finally admit they were there mainly to try and curry favour with the tribe than out of any real interest in the tribe's well being, and they leave the tribe.  Despite neither side getting an upper hand here, the Colt's still feel like they lost.

11. Ancient History
The Colts and Mossburg go to a bath-house to recouperate a bit, and talk about the past.  The two sisters manage to talk Mossburg into telling them about her exploits as a bounty hunter which eventually lead her to meeting their mother.

12. High Noon
As part of routine duties the Colt Sisters capture a group of thugs, one of whom seems particularly talkative.  He says that he's tired of getting the runaround from LeMat, and he knows that her side is going to lose.  He agrees to turn evidence against LeMat if the sisters can protect him long enough to get him to the nearest major city to turn him in to the prison there.  They agree, and load him on a train, only to be chased by pack of sundevils,  flaming hooved skeletal horses, who chase the train and attack it.  The two barely manage to fend them off, delivering their prisoner to the courthouse.

13. Showdown
With the testimony of the turncoat, the sisters finally have enough evidence to get a warrant to raid LeMat's home.  With the help of Mossburg, the sisters go to confront LeMat, fighting their way in and eventually capturing the land baroness.  Everything looks great, until they get back to the courthouse, where a Posse of Texas Rangers is waiting to arrest the sisters.  They realize, too late, that the lawyer in the courthouse they left the prisoner with was in cahoots with LeMat.  He claimed the sisters roughed up and tortured the confession out of the prisoner, who "died of his wounds in jail".  Everything the Colts have done so far is thrown out, and the trio(with Mossbur) barely escape.  Wanted fugitives now, they've lost everything.  With no choices left, the trio decide to track down their own posse of disenfranchised and wronged vigilantes, anyone done an evil turn by LeMat is now their ally as they work toward finishing LeMat's evil once and for all, no matter what it takes.  (this would comprise the second half of the season)