You can (and should!) help each other out by casting spells on one another, but you don't share resources, so you can't tap someone else's land for mana or cast spells from their hand
Whenever you add a lore counter to a Saga, check the number of lore counters it now has, and the chapter ability matching the new number will trigger
When you cast it, you get to gain control of a creature in play and then turn it into a 10/10, give it trample, annihilator 2 and haste until the end of the turn
Whats more, there are some pretty common threads in terms of colour identity
When you attack, Clavinelo turns one of your attacking vampires into a Demon, and gives them a permanent ability
For more information, please see the most recent version of the Magic Tournament Rules at wpn.wizards.com/en/document/magic-g (2021-07-23)