Obsidian is incremented in three scripts:
- bk3_fightengine.rpy
- bk3_maze.rpy
- bk3_tavern_quests.rpy
The tavern one shows obsidian as reward for quest 3 (firebender attack) and quest 7 (a peck of knowledge).
The script about the fighting system is a bit more obscure. It requires
occupied_room ==7, and is in label
bk3_after_fight_win, so it seems you need to have been in a fight. Examining the code and fiddling with the console in the dungeon, it seems it's the chest you reach by the following steps from the entrance: up, up, right, right.
In the maze script, one obsidian is given to you by Skye when you meet her in the dungeon.
One is found in the wooden crate with the hole the guards use for fisting when you hide in it and learn about its purpose the first time.
Two are in the skull you can find in one of the maze's corners.
Two obsidians are found jizzing on the headless statue's tits in the last section of the maze.
This should be everything.
Indeed the code for it is:
Code:
label bk3_home:
if nagina_free:
scene black
scene basingse_home_2
with dissolve
jump jdpregfuck
So the only check for jumping to that scenes seems to be whether you have the nagina_free flag.