Sidisi might be Commander-eligible, but it's better in the 99 of a deck
If the outside person you've chosen just refuses to play along, try to choose another person
A single Securitron Squadron isnt much to look at, but getting three or four off one card makes a large difference, and is excellent post board wipe
Creature Gandalf the Grey Whenever you cast an instant or sorcery spell, choose one that hasn't been chosen You may tap or untap target permanent
Fans can still pick up the Booster Box, four Commander Decks, and two-player Starter Kit for retail price or less
Focusing more on one or the other is important, because you either want to kill your opponent or just lock them out of the game