A bit of a backstory-ish info behind Zomu's unique magic.
Zomu has been known throughout history as "that guy throwing lava buckets everywhere". He (and Shaoron, in a bit later coming LPs) has a history of just burning every single person he comes across with lava during survival-based...
I absolutely adore how the author captures Zomu-san and Shao-san's relationship and personally I'm very glad that Zomu-san's very famous and very disastrous nature shines in the manga just as brightly as in the videos.
He's called "Ally's greatest threat" not for nothing.