A mass of evil energy was buried deep within Rhea's soul wisp, draining the Life Energy bit by bit. The damage was too severe because it took too long to get the proper help it deserved.
Not to mention the damage that took place over half of Rhea's body. It was frozen in solid green crystals because the curse was too severe.
The semi-transparent green crystals also did a perfect job of keeping Rhea alive, even though Rhea was still slowly going towards the death door. Lifa indeed tried every possible thing to keep Rhea alive.
Elysia and Elena also could see that the green crystal was a collection of life energy that might have come from Lifa, the tree of life.
