Crusader Kings III achievements

Restore the Roman Empire

Sleep with your best friend while having the "Ritualized Friendship" cultural tradition.

Create and upgrade a Men-At-Arms Regiment

Have your Dynasty rule ten independent realms of at least Kingdom tier simultaneously

Construct a new building

Appoint a Guardian to one of your children

While holding any Empire Title, be naked

Have strong hooks on three direct vassals

As Álmos Árpád, form Hungary and convert to Christianity

Have an artifact in every slot in the Inventory and Court

Have a new child

Start as Rurik the Troublemaker, 867. Lead your Dynasty to rule the Russian Empire