At the same time as the explosion, heat-resistant walls sprang up from the ground and encapsulated Ruby inside to contain the blast, but also to raise the temperature inside dramatically.
These walls, made of an ultra-hard alloy and stacked one on top of the other to form a thick, 15m thick shell, were not the result of Jake's skill, but a simple exploitation of his Purgatory Dream's creative functions. Even if the detonation were ten times more powerful, these illusory walls would have succeeded in confining the blast.
That said, even with this precaution, Jake still found himself breathless from the shockwave when he reappeared 100 meters away. Nearby adventurers like Elduin and his companions were blown away except for the large dwarf who managed to stay in place by rooting his heavy axe into the ground.
