Personally, I think that Mahjarrat are practically made using a form of Divination using Mah's energy. The crystals may or may not have been around before Freneskae was revised, and Mah may have found them just before creating Zaros and Seren. This could mean that they are practically divine crystal simulacrums, while the Mahjarrat are pure Elder energy scraps from her growing more tired, while having dreams of Zaros and Seren.
This could mean that the Ritual Marker is the crystal gods' way of channelling that energy around. In Seren's case, she was trying to return the Mahjarrat to the source in order to keep Mah alive, while Zaros' marker is designed to share the energy among them. This energy share would allow them to grow stronger with each ritual, while letting them endure.Prepare for hell on RuneScape in Naval Cataclysm!