Riki, a member of the mercantile Nopon race, is one of the seven playable characters in Xenoblade. That’s him flashing his fangs on the right. While Riki isn’t the protagonist he playfully says he was chosen as this year’s legendary hero.
Rein and Carna appear to be more battle ready. Rein is one of Shulk’s childhood friends and a Colony 9 squad member. He seems protective of Shulk too since he says won’t let Shulk get injured. Carna, part of Colony 6’s squad, carries a gun-like weapon and is skilled with projectiles.
Melia looks like Xenoblade’s resident magic user. She comes from Hienter, a technologically advanced society on Kyoshin, and uses ether attacks. In past Xeno games, ether skills were the equivalent of magic spells.