You know a cola addiction has gone too far when you wonder what would happen if you injected it.
Zephyr (due for a redesign). I can't say much about that drawing without spoiling something major, but read on if you're curious to see what I can say.
- The constructs rapidly deteriorate when they lose contact with her or the harness.
- She cannot create solids when she's not in direct contact with the Earth (so no creating wings and flying).
- While Earth ponies do accumulate this energy over time, using the harness swiftly consumes it; her use of the harness is limited by how much of this energy she has on hand. Overuse can leave her disoriented, drained, fatigued, dispirited, demotivated, or potentially dead.
There's another reason in her backstory that makes her use of this harness by orders of magnitude more potent than if another Earth pony used it; I won't spoil it, but I will say it's much more innate, symbolic, thematic, and meaningful than just me saying "Because I said so."
As a fun fact, her favorite, most powerful, but most costly thing to do with it is construct an energy bow on her back (centered on that gem) and fire arrows, using her tail to draw the bowstring. The projectiles have a low effective range, but if she happens to hit something with one...