In the survival world we have mobs every night and in caves its the same as vanilla however. with your strengh increasing the mobs around you follow you up never getting the fight boring.
Mobs can spawn with a level the higher the level the harder the mob and sometimes even giving them abilities.
How do u use it?
There is no need to do anything however its recommended to make a shield and wear armor if you are posing a treat to the mobs.
since they grow their level if you are killing a lot or wear a lot of high end items the mobs can also attack especially skeletons can be a pain if your not properly equipped