In the right conditions, this deck can almost play like a storm deck considering how much cost reduction you can get
Since Sliver Overlord is a legendary creature and is also legal in Commander, it can be your commander
Another thing the Swamp King appreciates is a player casting black spells, which means well want a high volume of black spells in the deck
Playing Shadrix Silverquill, you'll have fun choices to make each turn, either cracking deals or figuring out which power benefits you the most and how to let your opponents gain the least
It can amount to the accelerated life loss from a Phyrexian Arena, but it doesn't need to reach max speed so if you're stuck in second gear, you still double up on the staple black enchantment and good card draw
Acidic Sliver encourages other players to keep from messing with your Slivers, lest they eat a Shock, Heart Sliver is a cheaper Blur Sliver, and Homing Sliver can help you find the Sliver you need