Hearthpwn

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

9/10

This is the best "free" card we've maybe ever seen. Starting turn six four because this is druid we're talking about, you get zero mana 5/5s that hardly have a deckbuilding condition besides "put good cards in", since this always chooses the most expensive spell in your hand. Both Arcane Tyrant and Anubisath Defender both required the player to cast said expensive spell first, which at least limited the times they could be played. This, however, is just free. Not only that, with big enough spells, it actually GENERATES mana, of all things. Like Aquatic Form, I have no clue how on earth this got past testing. 

Kind of a... weaker Omu?

Even if there were a 10 mana spell in standard (there isn't) a 0 mana 5/5 past turn 6 isn't that great. This is basically Arcane Tyrant.

This is a more honest description of the card:

In Wild, probably yes.

Unbelievable..

its good but likely druid will still be running aggro for now

0 mana 5/5...

what the bleep!?!

Bonkers. Even if you just have a 3-cost spell in hand this is worth it, and the high roll of dropping two of these plus completely refilling your mana in one turn is crazy good.

Sigh.  More free mana, great.