This is the "Make-Good" event for the Limited Offer/Glitched Guild Bundle that occurred for roughly 2 hours when the cyberweek event launched on mobile.

For those 2 hours, anybody could purchase a bundle that gave all members of your guild 20,000 Titan Exp Potions, and 80 Summoning Spheres. Whether it was designed as a "doorbuster" Black Friday sale, or a glitch, we'll never know for sure.