A common question heard from new Xenoblade Chronicles players is "What are affinity coins used for?!" After all, you'll start earning these coins with every level-up and unique monster defeated, with no explanation of what to do with them! Well it turns out that Affinity Coins are used for setting up Skill Links between characters, and we've got your Skill Linking guide right here!
The standard skill tree, seen early on in the game.
As you find landmarks and defeat monsters, your characters will earn Skill Points (SP), slowly gaining access to new skills. Take a look on the skills menu to see the three branching paths they can choose from, and make sure to regularly switch which path they're on so that they develop the skills you'd like them to have most.
You'll first gain access to Skill Links after defeating the Arachno Queen in Tephra Caves. Open up the Skill Trees menu, then press the minus (-) button to begin setting up Skill Links.
Here, we see Shulk with three available slots for which to link Reyn's skills, the final two slots to be unlocked as affinity grows.
For each character you've added to the party, you'll be able to select skills that they've learned for other characters to use. First use R and L to decide which character to set up Skill Links for, then simply press the "a" button on one of the empty Skill Link slots beneath the portrait of the character you'd like them to link with.
In order to link the skill, you must have an appropriate number of Affinity Coins, and that skill must be the same shape as the slot you're filling (Circle, Square, Hexagon or Starburst). Take care to have your characters develop skills that are not only powerful, but that have shapes will fit into your open skill links!
Here, Shulk looks for a skill to link. Skills with glowing white circles are the right shape, though the red Xs all signify that the skills either haven't been unlocked yet, or not enough Affinity Coins are available.
Protip: Despite their name, Affinity Coins are not spent. Unlinking skills will return the coins to you, letting you spend them on different Skill Links. Don't be afraid to experiment!
As a note, the number of skills you can link from a character are limited based on the affinity between party members. So while Shulk and Reyn might be best friends, letting them swap out a full five skills with each other, Dunban and Reyn might barely know each other, only allowing access to a single skill between them.
So as always, help out your teammates during battle, think wisely during Heart-to-Heart dialogues, and always be making friends among your group. If you're good enough at both raising affinity, and collecting Affinity Coins (by leveling up or defeating Unique Monsters), your characters will soon be maxed out with up to 30 additional bonus skills!