Each other character which you unlock for your party have 2 primary Signature Arts that you need to unlock, before they can use it in the battlefield. To unlock these arts you need to complete a specific Affinity mission.
You will have company in Xenoblade Chronicles X during the battle against the enemies and monsters of Mira. There are total 18 different party members, which can join you in the battlefield. But first you need to complete certain tasks and requirements to unlock them.
In LEGO: Jurassic World, each character has a unique ability that makes him/her valuable in the game story. You can unlock many characters during the story, and if you want to play with them in the free play mode, you need to buy them. Some characters have 1 or 2 similar abilities.
There are plenty of playable characters that you can acquire in the story-line of LEGO: Jurassic World, level up fast complete the story levels and you can play with these characters. Many have special weapons and abilities that you need to complete the level and also to find hidden items.