Does a character know the effects of a spell when they are affected by it?

I have created a custom enemy, a golem desgined to investigate new forms of magic, and my players are about to face him.

Among several other stuff, this creature has two spells called high and low arithmetics. Upon failing a saving throw, this spell deals damage each turn to whoever ends their turn on a place lower or higher than the golem, respectively.

My question is, would a character, upon taking damage the first time, know what the conditions for taking the damage would be?

I’ve seen tweet but as far as I’m concerned, that only tells them that indeed, they are victim of a spell. Is there any way for a character to figuring out the rules of a spell? (not counting deducing them by trial and error, of course). I don’t think an arcana check (as is the common rule) would be suitable in this situation since this is a spell that none of them could have ever seen/heard of since it was made by this creature.