Your companions in Far Cry New Dawn can grow stronger just like you can. This happens in two ways: by upgrading the training grounds in your home base, and by keeping a companion with you for a long enough period of time, because they'll slowly gain new abilities while fighting by your side. This means you should have one of the eight companions with you everywhere you go, and without question that one companion is Horatio, the giant boar.
Leave everyone else behind. Yes, even the dog. I love dogs, but now I love a boar even more.
Why is Horatio so worthy of your constant company? Well.
He's a damn tank
Not one for stealth, Horatio will charge right in and begin knocking enemies down. Once down, he can stomp them for a kill. The third skill he learns is a sort of berserker rage where he'll blast right through a whole bunch of enemies, scattering them like sticks. And, as you see above, he can knock an entire damn truck onto its side. If you like hanging back and sniping, don't travel without Horatio the tank.
He loves rolling around in flowers
And yet Horatio is a gentle creature, too. When we get a breather from the action, he'll sometimes roll around in the flowers. I've seen him do it in the grass, too, and on dirt, but it's more blissful to see him flop to the ground and snort happily as he rolls in pink meadows. I bet he smells wonderful afterwards.
He takes out shielded enemies
My least favorite enemy type (not just in New Dawn but in general) is some dude with a big-ass shield. They deflect all your damage and block all your hits and then somehow they can still run right up and whomp on you! Unfair, if you ask me. Horatio isn't impressed with shields. If he goes after a shielded enemy, even from the front, that dude is losing his shield for good. Then you can pick up the shield and become a shield dude yourself.
It's fun to let him get the final kill in an outpost
When I'm down to one last baddie at an outpost, I'll usually just watch Horatio go ham on them. Sure, I could have finished off that biker with a saw blade, but Horatio is doing almost half the work, so it's fun to let him deliver the killing blow and unlock the outpost in slow-motion glory. He's humble, though. That little shake of the head. No bigs.
Sometimes he'll take a nap and snore a little
You'll have to turn the sound up on the gif above pretty high to hear it, but Horatio snores a bit. Sometimes during the rare quiet moments of New Dawn, he'll flop down on the ground for a bit of shuteye and have little piggie dreams, probably about eating earthworms or stomping Highwaymen to death. It's just adorable.
He'll revive you when you make a minor tactical error
Sure, all of the companions will revive you if they can reach you in time, but there's something about Horatio doing it, especially when you've made a minor error in judgement such as stepping directly in front of a speeding car to snipe the driver. It just feels better when you're saved from stupid death by a good-natured hog. I like how he doesn't seem to be in any particular rush, too. "Oh, look what this idiot human did. Again."
He makes dull conversations more fun
My reaction to most people talking in New Dawn is, "Yeah yeah yeah. Just put an icon on my map and I'll go brutally murder everyone standing near it." But I at least try to pay attention, and the nice thing about traveling with an enormous boar is they snort and snuffle and walk around in the background giving you something to look at. I'm not ignoring you, really, Pastor. I'm just enjoying the scenery.
He can self-revive and put out his own fires
Say you're a little bored so you're shooting at a tree with incendiary shotgun shells like a dumbass. And your favorite boar happens to be standing under the tree, and catches on fire. Unlike myself, Horatio is smart! If there's water nearby, he'll make a beeline (or a boarline) right to it and roll around to douse his poor burning body. You don't need to do anything but feel incredibly guilty.
Spend enough time with Horatio and he'll also learn to self-revive himself in battle, meaning you don't need to keep a close watch on him. If he goes down, he'll get back up without assistance, which is more than I can say for you.
He'll worry about you if you're out of his sight
Turn on the sound for this one. As I enter the house, Horatio loses sight of me and starts complaining. Freaking out, really. Kinda like if you leave your dog in the car and you go into a store for a minute, and your dog just stares at the door of the store until you come back? That's what Horatio does when you move out of his line of sight. It's touching! And noisy.
He'll follow you anywhere, no matter how stupid
Horatio can't ride in cars like the dog companion, but he'll follow alongside. In a chopper? He'll run along the ground. Jump off a cliff with the wingsuit and plow headfirst into the rocks because you forgot that you turn with the keyboard and not the mouse? He'll follow you then too. Loyal and non-judgmental.
He likes to swim around while you're fishing
Fishing remains an enjoyable pastime in the the Far Cry universe, when you can manage to do it without someone attacking you with a flamethrower. And it's even nicer with a hairy boar paddling around serenely in the beautiful water. I'm pretty sure Cheeseburger the bear did this in Far Cry 5, too, but boar beats bear, in my opinion.
Horatio can be found at Elsinore Farm, which is to the North East of Prosperity, right along the northern edge of the map. You might meet someone who tells you about him and marks his location, or you can just look for the farm yourself.