Like any other skill in The Sims 4, you have multiple ways to earn levels in Thanatology. If you plan on pursuing a Reaper career, then it'll be necessary to start studying for the sake of promotions.

The Undertaker may not be an active career, however, it does branch out to two different branches (Mortician and Funeral Director) as Sim gets promoted to level 6. With that, there is a bit of choice as to which skills Sim may want to improve,

There are plenty of spooky happenings around the world of Ravenwood in The Sims 4: Life & Death expansion, and if you've moved into one of the pre-made lots on the house, then you've no doubt noticed that starter tarot deck in your living room.

The Reaper career in The Sims 4 Life and Death brings a whole new perspective to the life of the Grim Reaper, as you become their protégé. Starting out as a Grimtern and working your way up to a fully-fledged Reaper isn't going to be easy, but thankfully you can head along to work with your Sim to help guide them on their way.