How many fetch lands you should include depends on a few things, but the short answer is often as many as you own
If there is a way to do Partner commanders right, then something like the Friends Forever and Doctor's Companion mechanics are the best way to go about it from a design perspective
Weight Advantage Conspiracy (Start the game with this conspiracy face up in the command zone.) Each creature you control assigns combat damage equal to its toughness rather than its power
Batching crabs, oozes, and horrors onto one creature that also cares about those types is fun, and I like a creature that makes copies of itself
Each creature you tap while casting this spell pays for or one mana of that creature's color.) At the beginning of each end step, if you created a token this turn, draw a card
The game's rules have frequently been changed by the manufacturer Wizards of the Coast, mostly in minor ways, but several major rule changes have also been implemented