Fusion
Ashton drank a Large Mana Potion as he created a formation that sealed the pocket dimension.
His attainments with Inscriptions are high, unfortunately, it isn't high enough to completely seal a pocket dimension. He's nowhere near strong enough to make something like that, nor did he have any materials to create a formation like that.
But, if it's just temporarily blocking outside influence, he could do it. And that's what he's doing right now.
"...it'll take...at least half an hour, for me to absorb this thing." He muttered while looking at the Dragon Vein. "This formation must last for that long or else this will become a huge problem."
Try as he might, he wouldn't be able to prevent the fluctuations from escaping and alerting the enemies above. Since the Dragon Vein was the real reason why they were here in the first place, it'd only make sense for them to have something that can monitor its activities.