Like most Magic: The Gathering cards, the value of Agent Frank Horrigan depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Fallout)
To make things easier for newer players, structure decks were introduced that contained cards necessary to make those strategies work
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
However, there was one powerful monster in the format that allowed Fish-type monsters to still have access to this powerful effect because Superancient Deepsea King Coelacanth is amazing at recycling resources
Like most Magic: The Gathering cards, the value of Cabaretti Ascendancy depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Streets of New Capenna)
When this card destorys a monster and sends it to the Graveyard as a result of battle, increase your Life Points by an amount equal to the original ATK of the destroyed monster