In order to obtain Soulare, you'll first need to get your garrison set up with either the Lunarfall Inn or Frostwall Tavern, and upgrade the building to level two. Once you have done so, you'll have an NPC in the building that can recruit one follower a week for you, and you can clarify what you'd like that follower to do. Soulare doesn't have a predetermined list of abilities, but players have reported obtaining him by looking for something to counter Wild Aggression, and by something to counter Magic Debuff. He is not a guaranteed option for either of these -- and since you can only recruit one follower a week, it may be quite some time before you see him pop up.
If you do happen to see him pop up in that list, you'll want to nab him -- both for his abilities, and for the fact that he can add to your Toy Box collection. If you target Soulare and emote /tired at him, he'll turn around and give you the Wayfarer's Bonfire. It doesn't have the appearance of a normal campfire -- it's a small bonfire on the way to smoldering out entirely, with a sword in it. If you click the bonfire, it gives a brief, AoE buff to everyone nearby -- nothing that actually boosts stats, just a visual effect. And to top it all off, it also acts as a cooking fire.
If you aren't in the mood to search forever for Soulare, however, you've got another option. You don't actually have to have Soulare in your garrison to obtain the Wayfarer's Bonfire. If you have a friend who has already obtained this mysterious follower, you can simply visit their garrison, use the emote on him and he'll hand one over for you. Like all other toys, the Wayfarer's Bonfire is account-wide, so once you've obtained it, you can use it on any of your characters. But if you're in the mood to try to obtain the elusive Light-praising knight, he definitely makes an unusual addition to your collection of assorted followers.