One is a sealed item printed by a manufacturer, the other is a digital purchase that assigns you a real, already-existing card from a tracked pool
It profits from all the cards that naturally go to the graveyard in a long, drawn-out game, and its a good evasive beater
Summary Rule-breaking Magic cards like Rat Colony allow for unique deckbuilding strategies and endless Rats on the battlefield
You can draw and then also toss a counter of the +1/+1type here for bigger and bigger digs from the tapping, so there is great internal synergy if you choose to mill yourself
Artist hncl designed Cynthia's Spiritomb with the idea that Cynthia's beauty would work in perfect contrast to the creepy and unhinged energy that Spiritomb always embodies
That makes it a great commander option, able to use lots of powerful cards that wouldn't normally find their way into EDH decks