I know there is this item you need to get, Ancient Tablets, and people even started receiving multiple of them. Is that why they were removed from the loot pool? I can’t get one to complete the quest.
Also can someone explain how crucible works? Does the second crucible opens if I get the stone tablet? I saw videos on Youtube where they went into a different crucible with chests hidden all over the level. Has that changed?
I am not sure what the video u are referring to is showing, but i am pretty sure its the loot room after the boss.
in the crucible you basically go from room to room while picking up buffs/perks on the way. In the middle there is a vendor where u can use the unique currency from killing enemies inside the crucible to unlock new things.
at the end there is a boss. if you are done with the boss and got your loot u can do it again. as it is rogue-lite it will be different for each run. different perks, different map order etc.
and what stone tablet do you mean? you get a quest in sacrament to talk to someone to open the crucible. not sure what it is called i am bad with names 
but i am sure someone will pitch in and help out.
The stone tablet was removed from inventories except one copy, but the quest remains open no matter how many times you finish it hr crucible at this time.
In the current version after being the crucible you clear rooms until the midway point where you are introduced to a new character and dialogue.
You carry on cleaning chambers until reaching EK, upon defeating it you get access to the last chamber, the loot room. This room used to contain the tablet in one of the chest, but does not any longer.
Hope this helps
thanks for pitching in, i knew i could count on the community to clarify what i missed 