Before Levin Cloud, Kabrakan and Solstice entered the hidden islands, Levin Cloud already messaged Adrian in the real world about their quest. He once again messaged him when they were tasked with killing a corrupted god fragment.
Levin Cloud wanted an insurance that they can at least mitigate the damage if they were to fail the first attempt. Adrian responded that he will now head to their location since his best friend asked him to. If he was completely confident, then Levin Cloud would not have asked Adrian that.
Levin Cloud and Adrian were banking on the fact that they could kill the corrupted god fragment using their synchro skill. It is the most powerful spell in their arsenal, and they already witnessed its capabilities once against a dark god.