Hibernation Sliver makes all Slivers very difficult to kill as long as you have life points and mana left to play with, and with all your creatures so cheap you would usually have plenty of both when it counted
You know how lifelink causes you to gain life
Cards like Phlage and Detectives Phoenix give you a ton of natural resilience, and with Cutter in the mix, you can rebuild a board presence at the drop of a hat
Start with at least 10 counterspells as the number of counterspells you should play in Commander, and it really depends on the deck youre building
However, it is unique in that there is no life cost to playing this untapped
Theres a real argument to be had over which card is more powerful between Brutal Cathar and Skyclave Apparition, and while I imagine Skyclave Apparition wins out in most scenarios, it is worth noting that Brutal Cathar can nab multiple creatures if you are able to transform it multiple times