I wanted to take another stax deck, this time with Derevi. I'd sort of flirted with the idea in my other Derevi deck, but I figured I should make a decklist where I go whole-hog with it.
The main synergy the deck is built around is winter orb/rising waters/hokori, dust drinker. Derevi is doubly brutal because he can not only untap your own lands, but also tap down your enemies' so they never have more than 2 mana.
What about World Queller, Cataclysm, Tangle Wire, Smokestack, the Rishadan critters, or a few more wipes to force opponents with explosive starts back into your grasp?
I love smokestack in my glissa deck, but this deck doesn't really have good sac fodder for it (with a few exceptions). Derevi himself is ok but 4 a turn is quite a bit, and usually I find it's necessary to ratchet it up to 2 before it gets nasty. Similar situation with worldqueller.
Cataclysm is very strong in the right deck, but I don't see how this could possibly be it, all the creatures are weenies, and the deck's biggest strength is its ability to make all but 1 of my opponents' lands useless already.
The Rishadan creatures just seem weak for EDH.
Tangle wire is OK but I don't see any particular synergy with Derevi. It's kind of nifty with winter orb and co but not worth it imo. I've been less than thrilled with it in my glissa deck, and she's got lots more synergy with it.
I don't keep decks together for more than a few months at absolute maximum, and usually just a few weeks (With notable exceptions of Zirilan and Phelddagrif, which are my perm decks). This one has been disassembled for almost 4 years.
Offhand, though, topplegeist seems like a pretty solid inclusion, as does siren stormtamer and selfless spirit. To give a better answer I'd probably have to dig through my boxes, good chance I'd change a lot of cards but Derevi isn't a commander I'm likely to build in the near future (and if I did, it'd probably be something totally different than this list).