With the black pillar standing between Pangea and Gehenna, only those who could withstand the gravitational pressure could travel between the realms.
Only the strongest beings were granted passage, no matter how big the opening.
At the very least, that would continue to be the case as long as the black pillar wasn't destroyed or the crimson light domain didn't expand.
Vaan was quite confident in the sturdiness of the black pillar. But after learning about the Asura Law, he was not so much anymore. Whether Abaddon could destroy the black pillar remained to be seen.
However, based on his estimate, he had about thirty minutes until the small shifts in the black pillar left a slight opening of the crimson light domain, connecting the two realms.
'Half an hour… What can I do to increase our chances of survival and victory?' Vaan mused.