For the most part, these function the same as sagas normally do, giving you chapter abilities for each turn that they remain in play, except they can also attack and block just like normal creatures
For some time, this was the premier example of this mechanic, as this card saw some play in various Infect decks in Modern as an answer to Card not found
#9 Gemstone Caverns Gemstone Caverns has only becoming a more popular option in Modern as of late
Creatures (14) Lands (25) Spells (21) Note that this is just one of many possible configurations for a new Standard Jund deck
Casting spells and activating abilities are key to the game, and they're not happening if you can't pay for them
It has some strong effects, but enough of a strong effect for 9 mana