I am not sure what the description of Magic Jar means by “class levels” and “class features”:
[…] Once you possess a creature’s body, you control it. Your game
statistics are replaced by the statistics of the creature, though you
retain your alignment and your Intelligence, Wisdom, and Charisma
scores. You retain the benefit of your own class features. If the
target has any class levels, you can’t use any of its class features. […]
For example, if I possess a Gnoll, do I gain the benefit of its Rampage feature? Is that a class feature?
Best Answer
'Gnoll' is a race, so unless Rage is specifically called out as a class feature, it would not be included in the above description so you would get it.
A class feature is a feature you get from your class. This would include spells from a Wizard, extra attacks from a Fighter, sneak-attack from a Rogue, etc. Abilities that a possessed creature would get as part of its level progression are NOT conferred to you by Magic Jar. Furthermore, the spell is telling you that your retain all of YOUR class features (your spells and abilities granted to you from your class). So if you as a Wizard possess a Fighter, you would get the Fighter's physical stats (STR,CON,DEX), keep the Wizard's mental stats (INT, WIS, CHA), and also keep the Wizard's class features (spellcasting, Magic School Specialization, etc). You would NOT get the Fighter's extra attack, nor would you be able to use any of the Fighter's combat maneuvers.