Alternatively, just play a death domain cleric.
I don't think that there's a Death Domain Cleric subclass ... yet ...

BTW - it is easy to become Oathbreaker before lvl2. After leaving the Nautiloid do NOT go up a level, but go and talk to the Thieflings, whom you stab in the back to lose your Oath, then go to Camp and talk with Groundsman Willie, become an Oathbreaker, and only THEN level up.