You can mutate Snapdax, Apex of the Hunt onto Phyrexian Crusader for example
It allows you to untap and play even more spells
Lets apply this concept to a specific example, the Stone Tongue Basilisk deck: 1-cost cards: Llanowar Elves, Fog, Rangers Guile, Giant Growth 2-cost cards: Rampant Growth, Mulch, Grisly Salvage 5+ cost cards: Natures Revolt (costs 5), Stone-Tongue Basilisk (costs 7) In this example, the distribution would be 16 cards with a mana value of 1, 12 cards with a mana value of 2, and 8 cards with a mana value of 5 or higher
The 'cards in hand' thing is the lamest text I can find on a Magic card
If you get lucky enough to draw A Whole New World again in your third hand
You need to have some redundancy for a lightning-rod equipment in play