Distinguishing constructs, elementals and undeads

The monster types mechanic in D&D has always been iffy due to the arbitrary definitions and distinctions between the monster types.

For example, the [fey] type is an amalgamation of many different concepts from mythology and folklore. It include Greek rustic gods (dryads, nymphs, satyrs), Celtic nobility of the Otherworld (seelie and unseelie courts), Celtic tricksters (sprites), fairytale hags, the ghostly fairy dogs of the British Isles (blink dogs, yeth hounds), and “celestial fey” invented for Planescape (eladrin, guardinals).

Another example would be the distinctions between the [construct], [elemental], and [undead] types. Although they are self-explanatory, it is very easy to devise monsters that straddle more than one of them or stretch the definition. This reveals weaknesses of the mutually exclusive tagging system.

Creature Collection Revised features the [elemental] “strife elemental.” The strife elemental is a personification of an abstract emotional concept rather than a physical classical element. What else would you type it? [demon]? [monstrosity]? Those are poor fits.

Forgotten Foes features the [elemental] “junk elemental.” The junk element is a spontaneous personification and animation of an artifice, in this case thrown away junk, rather than a simple classical element. It clearly straddles [construct] and [elemental].

Legends & Lairs: Elemental Lore features the [elemental] “last breath.” The last breath is an air elemental animated by the spirit of a dead person, the animated literal last breath. It clearly straddles [elemental] and [undead].

Creature Collection II: Dark Menagerie features the [undead] “siege undead.” (Monsters of Porphyra reprints it as “besieged undead.”) The sieged undead is constructed like a construct from the parts of a corpse, separating the skin, muscles and bones into three separate constructs with other materials (like sand, wood, nails, and wire) to fill the gaps. It clearly straddles [construct] and [undead], if not wrongly typed and more sensible as [construct] to begin with.

Creature Collection III: Savage Bestiary features the [construct] “spontaneous golem.” (Monsters of Porphyra reprints it as “spontaneous construct.”) The spontaneous construct arises naturally (or supernaturally) from crafted objects like pelts and gallows, but never deliberately created. It clearly straddles [construct], [elemental], and [undead], for all the same reasons mentioned prior.