Is the Blood of Ch’thon a limited item to get or am i miserably unlucky from 5 shots at it, i got it only the first time and then, nothing more??? I need it to craft the Skeleton Key cause the game crashed as soon as i finished the fourth level of the Steps of Torment ( Suffering ) and really pissed me off 
It has a chance to drop from Chthonic heroes and treasure troves. You can use the blacksmith in Necropolis to exchange Ancient Hearts and Tainted Brain Matter for Blood of Chthon.
Bring some blue items to Darlet and some dynamite… you’ll get a rare material eventually
If you didn’t kill the snitch in Devil’s Crossing he gives you a key for Depraved Sanctuary. You can get a lot of Blood from heroes in there. (If you didn’t know this already)
I have two toons that have access to the Depraved Sanctuary, and one I killed the snitch like an idiot.
Strange Key can drop from Bloodsworn enemies in the Act 1 areas. I usually kill him in the first two difficulties and then let him live in Ultimate. He will be an extra Cronley hero in the Cronley Hideout, helps in getting bad reputation to unlock Fabius.
It’s hit or miss to me. I’ve created a boatload of characters and some will get lucky and have like 7 Blood of Chthon along with a healthy number of ancient hearts and tainted brain matter just after a playthrough of veteran, and then another time I had a character that had only one Blood, zero ancient hearts, and only 1 tainted brain matter and it felt miserable farming for any one of those three.
As pointed out you can craft (basically exchange one of these three for another) Blood at the blacksmith in Necropolis.
Another one that’s hit or miss is Chtonic seals, where I might not gather the three needed for the faction quest all the way up until Necropolis when I’m unlucky, or I might get like a couple dozen of them before I even reach Blood Grove if I am lucky. In some playthroughs I have seals coming out the ass, then for some unlucky playthroughs I’m desperately wanting one to drop while I’m grinding away in Necropolis for a quest I should have normally finished around Blood Grove/Darkvale.
If you’re starved on all three of these item types though, to me the least miserable way to go about it is not set your sights on any particular item and just skip quests for later. The game can become really miserable if you’re hunting for an exact item – when you’re not you can find later that you have a number of them.
Also you get one at least early on in act 1 if you do cultist’s orders and kill Direni, which is also nice since you don’t have to fight him repeatedly after that in Cronley’s Hideout if you do Cronley runs for dynamite or rep or just farming Cronley.
Go to the portal “Prospectors Trail” and run a few steps to the south. You’ll find the entrance to the “Mountain Deeps”. There are 3 spawn locations for a treasure trove. You have a great chance for TBM, CB or AH. Just bring dynamite. As previously said cyou can exchange these 3 materials in the necropolis (skeleton blacksmith guy).
You need 5 minutes for this run. I did it a hundred times 
There is also a picture somewhere of the 3 spawn locations. They are really near to the entrance of the cave.
^^ This I love to do. But you do it in veteran/elite? I usually almost skip treasure troves in veteran, kind of go for them in elite if they’re on my way to something, then only do runs in ultimate. I didn’t think the drops from the troves were worth the dynamite so much in normal/veteran. Do hearts/blood/brain matter drop often enough even in veteran/elite?
For me I like to go to black legion and pick up a mountain depths bounty on the way before going each time, then can gain some BL rep and trove at the same time… though if I find the trove first before Ikrix or Sicrix, just restart and go back to mountain depths… only fighting them if I encounter them checking the trove locations.
I do it on ultimate with my dual wielding pyromancer. I did not try to run this on veteran/elite. Im also just hunting for treasure troves on ultimate in general. Did not have the need to explicit farm those materials before ultimate.
btw great idea with the bounty to gain some rep !
These can be pretty annoying to get, but not impossible. As others have mentioned there is the Direni quest which comes from a book stand in the building just north of the Burwitch town portal, need to select the Kill Direni option, though as mentioned he is worth more alive in ultimate than a single blood. There is also a quest in the south of rotting croplands near the Rover camp which requires dynamite to get into a cave with a little girl in it, follow the dialogue options and if you call her out on her BS you get one as a reward.
The best way to get bloods though is to get Darlet to blow legendaries up with dynamite. Just get a character that can complete the crucible with the 6th spawn up and you should get several legendaries a run on any difficulty. As for dynamite supplies do Cronley’s Hideout, Staunton Mine, or Fort Haron runs, some of which you need to do for nemesis rep farming anyways.
Having said all this, I just don’t see the point in running Steps or Bastion before max level as I’m sure you’ve realized bloods are pretty precious so why waste them on Elite where your item drop chances are significantly lower and it costs the same on Ultimate. Just do the quest to get the keys and save them until you are ready to do a full run.
Wait really? Because my experience has been that the cult hands them out like fliers. I think I have around 70 sitting in my bank right now and any time I go through a zone with a lot of cultists I end up with ~10 more. Maybe I’m just lucky with these things (and what a dismal thing to be lucky with; wish it was blood of cthon or any other useful thing).
Um, if you’re farming Cronley rep then leaving Direni alive means an extra 150 rep on every run. Having another guaranteed faction boss in your faction dungeon is hardly something you want to discourage.
Uh, yeah, which is why he said “if you do Cronley runs for dynamite or just farming Cronley.” i.e. not running it for rep, just running it for dynamite and/or Cronley’s ring.