Balmor, Battlemage Captain Wizard decks have gotten many boosts over the years, especially ones that specialize in casting instant or sorceries
As well as being one of a number of great five-color sliver commanders you can put in your sliver EDH deck, Sliver Queen is perfect for quickly building up your board presence, shooting out multiple slivers in a turn without using up your precious cards
More than others, Sidisi, Brood Tyrant is the commander I see as the general placeholder for Sultai graveyard decks
But Ill skip ahead to the most important reason, and its right in the title of the game
As for creatures I think Sapling of Colfenor would be good
The blue Dominus plays defense well, and it can even convert spare loyalty counters into an indestructible counter for itself