Payday.

They can't do anything to each other for the moment. But if a clone gets into a disadvantageous situation like being in an Apocalypse weapon and can't get out on his own, the rest might decide to seal him so that he won't be a threat to them anymore.

This is possible because they don't trust each other. If it happens, the worst thing he can do is stop using the Aspect of Unity and withdraw his Supreme law from Legion-0. While that will weaken them, it will weaken him more. After all, he is just one while they are 11. 

So in this mission, the entities he fears the most are the other clones, not the first sage, who will be very angry with him soon. He was thinking about that and chuckling to himself in anticipation as he infected the Apocalypse weapon. 

If the first sage had built the Apocalypse weapon with his Supreme law as its foundation, he would have noticed the infection problem immediately.