The Magma Maelstrom shard reduces the charge time on Fissure of Embermount, allowing it to produce Molten Power more quickly.  Yet its wording makes it sound like it worsens the charge time on Fissure of Embermount.

The current wording: "Rate at which Fissures of Embermount generate Molten Power is reduced by X%"

If I may make a suggestion, try:  "Decreases the time it takes for Fissures of Embermount to generate Molten Power by X%"