Chapter is... 4
Card Number is... 87
So today's card is Garnet (2)!
Remember, Garnet is a restricted card name! You can only have up to 3 cards named Garnet in your deck.
That said, this Garnet is an impressively efficient card! For only 2 Aqua CP, you get to play a 2 CP Summon of any element from anywhere in your deck and a cheap Blocker!
Strangely, there's no cost 2 Aqua Summons in Chapter 4. But looking at other chapters, there are many cheap, efficient Summons like Fairy or Ashura. You may even consider having single copies of some of the more circumstantial Summons, like Leviathan (2) or Adrammelech, the Wroth (2), since you be can be confident that you'll be able to use Garnet to pull the one you need out from wherever it's hiding.
If you have a Summon heavy deck, there are better Garnets out there, but in a Summon light deck, Garnet can help you get your nice Summons out much more reliably.
If nothing else, Garnet showed me how nice some of those cheap Summons could be!