So, I guess familiars were changed in the final version. Originally, they were lost forever if they died. Now, you can get one back when you level up.
Any particular reasoning for this change? Was it because of the Warlock’s class feature?

I actually developed the rule when I was working on shaman’s totem animals. I liked it so much I added it to familiars.
The setting justification, in my mind, is that the familiar is linked to the power of the caster, so it makes sense that as he grows in power he would have an opportunity to regain a lost familiar.
The actual play justification is that ACKS is a frickin’ brutal game and keeping a familiar alive is hard.

Ha! Indeed.