How is the materia modus supposed to work?


Im new to the game (xbox) and have been having trouble with the materia modus in upper erebus. I have to rescue Meridian from a cave, but every time I put, or throw, the mana core in, it burns for a moment and nothing seems to happen. The quest also keeps the objective, so I don’t know if I’m going to the wrong one, if i need more cores, or if i need to wait for a certain amount of time. Any information would be helpful.


Yes it only flares briefly but you should here more noise than just the flare.
What is happening is that a water level is dropping - If you are (I’m on PC so hope it is the same) standing down to the left of the caged room (with the stairs down and a spell etched on them) at that modus…then toss one in then go directly down again where the water was…it won’t be there anymore. It doesn’t even matter if I have the wrong map or the wrong quest - all the materius ever does is lower or raise water levels. Pretty important.