Opponent threatening to combo off
There are a LOT of ways to protect our creatures from Clot Sliver to Crystalline Sliver, ways to go over blockers with Winged Sliver, and ways to do enough damage like Megantic Sliver
This kind of grindy, variance-heavy self-mill plan isnt going to be as explosive or consistent as some other popular Commander decks, but I know there is a set of players out there who love to play a methodical and reactive style, and Winter lays out a really cool way to do that
If you cast a spell this way, pay life equal to its mana value rather than paying its mana cost
You can see white dots and dirt in certain spots
With Ashnods Altar and Nim Deathmantle, you can loop Caller in and out of the graveyard to generate infinite 2/2s and infinite mana