Its a long-term threat out of the graveyard for when you can afford to escape with card type duplicates
For both of these reasons, my wife really liked the card catalog
The cards are designed with their mechanics first in a spreadsheet, with rarity assigned according to certain stats and text
Heart of Kiran takes a hit since Thorn Lieutenant cant outright crew it, but this impressive card replaces itself if destroyed, cant be targeted or pushed around by aggressive creatures, and it protects from flooding late in the game by providing a 6/7 attacker fore five mana
this type of repeated creature generation works nicely in a sacrifice deck, where you can let those Snails serve a higher cause by making mana or being used for spells
City of Brass makes you take one damage when it is tapped and can give you one mana of any color in return and, likewise, Mana Confluence adds one mana of any color but has the requirement of paying one life