This is another strange rule to me because it seems that you might want to move a character off of a location altogether
Sadly, I think Varchild gets overshadowed in theming by Xantcha, Sleeper Agent, whom we will discuss very soon, and is a good design that just never got a chance to gain widespread attention
Thats not the case with The First Sliver, which oftentimes doesnt even run another Sliver creature in the deck
Prize cards are both a way of monitoring how close a player is to winning with one of the victory conditions in the trading card game being to draw all your prize cards first and an avenue for players to draw more cards into their hand
While it has no immediate impact upon hitting the battlefield, when you start attacking, you put a +1/+1 token on each attacking creature
Also consider Mana Echoes for an easy 2-card infinite