Normally, Xiantian Emperors wouldn't be able to fight against Saints but Don Don is confident that his disciples would be able to stall for time.
The people of this world cannot fight with all they got since they can't recover instantly and if their dantian became saturated, they would be absorbed by the world consciousness.
Don Don know this after going after different worlds throughout all of this time, with the amount of knowledge they had acquired, he instantly recognized the problem of this world.
He is also a chosen one, with the effect of the Murim World's consciousness, he is quite sensitive towards the energy of other worlds and how it operates.
That is why, he is confident that his disciples which have been sparring with Saints to improve their combat strength could hold on for a couple of hours.
Sans might not arrive in this timeframe but the reinforcement from Murim World would certainly would.
