After many adoption attempts, I have only recently become a loving father to a boar in Valheim. It's both a blessing and a privilege, but I feel like little Hammy Wammy needs to loosen up a little. Get a bit of fire in his belly, you know? As always, a mod has come to the rescue, and this one lets you tame and breed creatures that aren't normally tameable, like trolls. Finally, my boar son can learn from the worst.
A viking tamer by the name of "buzz" has created a Valheim mod called "AllTameable", which lets you tame and breed creatures which aren't normally tameable. By default, this only includes trolls and goblin brutes, but if you're willing to do some config file tweaking, a huge number of nasties opens up: trolls, skeletons, leeches, almost any beast your heart desires can be domesticated. Yes, that includes a number of the bosses too.
I say "almost" because a few creatures still can't be tamed. Oddly enough, many of them are the most docile of the bunch: deer, fish, gulls, and crows, for example. You can see the complete list of creatures you can and can't tame in the mod's posts section.
One of the things that makes me happiest in Valheim is seeing my children happy. Nothing compares to seeing love hearts spring from Hammy Wammy, or big yellow letters announce that my bees are happy too. And I'd love for a large, blue troll to join their ranks. I may need to sleep with one eye open, but it'll be worth it for the big hugs I'd get.
It's also worth noting that if you want to tame other creatures, I'd highly recommend reading through the Buzz's step-by-step guide in the mod's description section first, as it requires some finicky config file changes.