Its easy to discount the value of the death trigger, however
It is effectively instant
The problem, of course, is that theyre strictly worse than Unknown Shores, which is hardly a staple
Second, the player with the initiative ventures into Undercity again at the beginning of their upkeep
Will Scourge of the Skyclaves die, because it doesn't have the ability and is a 0/0 or does it immediately becomes a 1/1 to stay alive
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as a flashback cost), add any cost increases (such as kicker costs), then apply any cost reductions (such as that of The Water Crystal's first ability)