@Liquidxlax The arithemetic goblin was probably nearby when a goblin with super strength passed away, so he inherited the skill.
The whole chapter is a little bit strange on that front, as it's unclear how name inheritance encourages goblins with similar skills to hang out.
He probably should have told the party they're ridiculously under leveled for that serpent battle once they were out of the village chief's earshot. This dumb party would probably still think he's just a jerk, though.
@Moraza He should have gone with a cheesy abjuration wizard build, with shield, magic armor, and alarm. If this is 5e. If this is an older edition he can just stack buffs and save or suck/die spells.
@keioskod he probably thinks filia is why he didn't choose a similar path; it's probably more the concept of a childhood friend to keep her company despite her negligent family.
@iamagaroze If I had to guess he'll arrive after the tournament is complete and a great master is accepting his boys as pupils, state that he won't allow someone who can't defeat him to teach his children, and completely curb stomp the master. And just think his boys were being fooled by a weakling.