Is it common, can you do it during character creation, do you create a test of mettle or have one handed down from the egregore for example. Thanks in advance!
There is a process for creating a new noble house, but it’s mostly for creating them in play.
During Character creation it is basically just come up with a name and a concept, and as much backstory as you like. If you are playing a noble it is worth coming up with a test of mettle.
Have an idea of where you came from (people will ask, because that’s fun), and why you have chosen to come to Anvil now.
Set your own tests, think of your own traditions and why they have developed. Why are you Proud of your House? What makes them stand out? Which region do they hail from? Why would people want to Test into your House?
Basically, you can create pretty much anything as long as you fit within the brief. The egregore - and other players - can give you advice if you need but mechanically it’s just a matter of filling in the right bits at character creation and then going for it in uptime.