What are some "secret" unlockables no one talks about?

I'm sure everyone knows this one by now, but the "child of the island" trait allows you to summon and interact with island spirits on Sulani, and if you manage to befriend one long enough to get them into your household/get their relationship bar high enough, offspring will inherit the "Sulani mana" trait, which lets them summon volcanic bombs at will, which is a pretty cool visual effect lol.