Multi-type monsters

Both 13th Age and 5th Edition use "types" as a quick means of identifying and targeting monsters.

• 13th Age has Aberration, Beast, Construct, Elemental*, Demon, Devil*, Dragon, Giant, Humanoid, Ooze, Plant, Spirit** and Undead. (*13 True Ways; **13th Age Monthly)
• 5th Edition has Aberration, Beast, Celestial, Construct, Dragon, Elemental, Fey, Fiend, Giant, Humanoid, Monstrosity, Ooze, Plant and Undead.

I think that is a decent list that covers a lot of ground while being easy to tweak. A little house rule I would use is that a given monster may have multiple types as appropriate a la Dark Dungeons or Fantasy Craft. These would be separated by forward slashes: e.g. a chimera of goat, lion and dragon would be [Beast/Dragon], or a fey like the nymph or satyr would be [Humanoid/Spirit].