White Rhystic Study Although mono-white card draw has been getting better recently, White Rhystic Study would still be a great inclusion alongside a mono-white Commander
Provided you can crew or saddle with it, or get in for a free attack, you can turn on the extra mana tap
Maybe your opponents played their own Docksides Extortionists and racked up a few Treasure tokens that way, or they created their own through some other means
If you earthbend a fetch, it comes back into play after you sacrifice it, which allows the Cub to be a Rampant Growth, a substantial landfall enabler, even a source of sacrifice fodder
I don't think any other sliver creatures are worth it for this combat-focused version of Slivers
5 Alakazam Ex $42.92 This Alakazam special illustration is very close to becoming a rainbow rare with the number of colors present in the foil