The cards are designed with their mechanics first in a spreadsheet, with rarity assigned according to certain stats and text
For instance, in an Archimandrite deck you could gain a bunch of life in your upkeep and first main phase to add a big +X/+0 buff to your commander, then use Alteration to turn it into Giggling Skitterspike
This card serves as your "commander" with unique abilities that make plays even more powerful INCLUDES ACCESSORIES AND DECK BOX: Also comes with 10 two-sided tokens, a deck box for storage, and punchout counters to keep track of creature buffs For Fun I think Grave Danger is the most fun of these precons as-is
If you go over 13 mana value, you dont get to cast the spells you exiled
Then, at the beginning of combat on your turn, you get to put X +1/+1 counters on another target Creature you control, where X is the number of experience counters you have