Hearthpwn

Always hits the lowest cost spell in my hand 100% of the time. I'll have a hand full of 6+ mana cost spells and 1 low cost spell and this will always 100% of the time hit the lowest cost spell. Is this card designed to do this? Bug maybe?

Mistermath's Card Ratings for Voyage to the Sunken City:

5/10

A 3/7 taunt is worth slightly less than 5 mana, making the card extremely reliant on its effect. Unfortunately, the conditions are just too specific to make work outside of a select few metas, as you need to have only high spells and you need your opponent to only have low spells for this to work.

lorewalker cho, local shark, mailbox dancer. banana vendor, mukla… hmm… i’m gonna try a meme deck that mills the opponent with cheap spells then play this lol

This could be very interesting if you just run a few high cost spells, but a dead card against a lot of aggro decks.

Imagine playing this minion when you are Cult Neophyted, or even Loathebed with shudderwock.

Priests can literally make opponent's spell unplayable if they play this when they have the shard of naaru in hand with a mana cost increase effect. It is too conditional but i am pretty sure i will watch it happen on youtube.

will big spell mage like this?

Well uh, it's possibly very disruptive.  Or you could help them.