Okay, but I can make this exact case about ghost types and grudges/possession, and that's what I was getting at. Not that grass types using photosynthesis is cliche - grass types are great - but that pokemon with wildly different designs can have some common threads.
Upon review though, I was actually overstating how common those themes are in ghost types. Most of them don't mention grudges or possession at all. I'll run through them, to add to your eventual thesis notes
:
- Gastly/Haunter/Gengar are about gas and shadows
- Misdreavus is a wailing trickster that absorbs fearful feelings
- Mismagus is about incantations, both good and bad
- Shedinja is a hollow shell, believed to steal your spirit if you look into its back
- Sableye eats gems. Again, hearsay says they steal spirits
- Shuppet is drawn to and feeds on grudges and negative emotions, though isn't born of them
- Banette is an abandoned doll or voodoo doll, and for sure is born of grudges
- Duskull is a grim reaper, which doggedly pursues & spirits away
- Dusclops is a mummy, eats will-o-the-wisps
- Dusknoir travels to the spirit world, guides lost spirits
- Drifloon is made by spirits of pokemon and people, sometimes spirits away
- Driblim is just a big ol' hot air balloon, doesn't do ghosty things
- Spiritomb is 108 spirits bound to a keystone for past misdeeds
- Froslass is a yuki-onna, rumored to be formerly a woman who got lost in the mountains
- Rotom possesses objects, but not permanently, more like a poltergeist
- Yamask are spirits of people interred in graves
- Cofagrigus is a sarcophagus, said to turn people into mummies
- Frillish and Jellicent are basically jellyfish. Jellicent likes to eat life energy
- Litwick family steals life energy to fuel their flames
- Golett/Golurk are just golems, implied to be made by ancient science
- Honedge family are possessed swords that steal life energy from wielder
- Phantump are possessed tree stumps, supposedly by dead child spirits
- Trevenant is mostly about controlling trees, using roots as a nervous system
- Pumpkaboo is kind of a possessed pumpkin, carries wandering spirits
- Gourgeist sings a lot and curses people
- Mimikyu is a cutie pie
So now we have Sandygast/Palossand, which are sandcastles and moving sand (that's new), possessed objects (shared with Banette, Honedge, Phantump, Pumpkaboo) born of grudges (shared with Banette) after pokemon fell in battle (actually the 1st reference of pokemon specifically
falling in battle and becoming a ghost pokemon, so they're not peaceful spirits), that control people to add material to them (that's definitely new), and feed on life force (that's shared with Jellicent, Litwick, Honedge, and maybe others, though I like the detail that people ritualistically put their hands in Sandygast mouths as a test of courage, which evokes bullet ant nests).
The common threads aren't the problem, but how you twist them and weave them into something interesting, which most of those pokemon do; in the list I made, there are only two, three pokemon with photosynthesis as a main aspect (sunflora and leafeon, both well justified; fomantis too.
However, take a look at the ghost pokemon, of which there are less than the grass types, it bears mentioning.
I'm bolding the common threads;
magenta is "trickster",
red is "consumption of life in any form", "kidnapping" is
blue (even though ostensively, it could be in red, assuming the people end up dead),
orange is an origin related to something tragic,
green is possession.
- Gastly/Haunter/Gengar are about gas and shadows
- Misdreavus is a wailing trickster that absorbs fearful feelings
- Mismagus is about incantations, both good and bad
- Shedinja is a hollow shell, believed to steal your spirit if you look into its back
- Sableye eats gems. Again, hearsay says they steal spirits
- Shuppet is drawn to and feeds on grudges and negative emotions, though isn't born of them
- Banette is an abandoned doll or voodoo doll, and for sure is born of grudges
- Duskull is a grim reaper, which doggedly pursues & spirits away
- Dusclops is a mummy, eats will-o-the-wisps
- Dusknoir travels to the spirit world, guides lost spirits
- Drifloon is made by spirits of pokemon and people, sometimes spirits away
- Driblim is just a big ol' hot air balloon, doesn't do ghosty things
- Spiritomb is 108 spirits bound to a keystone for past misdeeds
- Froslass is a yuki-onna, rumored to be formerly a woman who got lost in the mountains
- Rotom possesses objects, but not permanently, more like a poltergeist
- Yamask are spirits of people interred in graves
- Cofagrigus is a sarcophagus, said to turn people into mummies
- Frillish and Jellicent are basically jellyfish. Jellicent likes to eat life energy
- Litwick family steals life energy to fuel their flames
- Golett/Golurk are just golems, implied to be made by ancient science
- Honedge family are possessed swords that steal life energy from wielder
- Phantump are possessed tree stumps, supposedly by dead child spirits
- Trevenant is mostly about controlling trees, using roots as a nervous system
- Pumpkaboo is kind of a possessed pumpkin, carries wandering spirits
- Gourgeist sings a lot and curses people
- Mimikyu is a cutie pie
This list is one you made, so from all your knowledge of these pokemon, these are the most remarkable features you could recall. As you can see, they already repeat a lot, and I could add more, too, like how Froslass
encases people in ice, or Gengar
scares people, or people who see Mimikyu without the cloak
fall ill.
Now, let's add a few more entries, shall we?
- Sandygast steals life force, possesses children to build itself up, and is born from the grudges of pokemon.
- Palossand possesses people to build itself up and hunts for prey with a radar shovel.
- Giratina was banished for its violence, and lives alone in a parallel dimension. (maybe it could be red, but I'm not sure; it's borderline)
- Hoopa steals things from people, and has a very greedy and violent real form.
Again, repeated threads. Each one of these pokemon
is original, in the sense that none of them has been done before, certainly; but originality doesn't guarantee your idea will be rich; that will be your execution; the litwick line, for example, is as boring as the sandcastles; people just ignore it because they look cool and are strong and another unique typing (and hey, golett and golurk exist; I just realized now these two don't even have that originality in their favor); even I didn't notice that when they came out; only now I'm starting to notice the reliance GF has on these tired tropes, once I could get past the unique weaves they use them in to see the threads; this time, I'm just seeing bare threads, not a unique or interesting pattern using them; if I had to get more precise, sandygast is worse, palossand is just boring, and I need more than the image of one eating a pikachu (as satisfying as that is) to overlook how bare-bones it is (something I already do very often).
Now, there's a reason why most of those pokemon, despite using common threads, don't cause so much noise as the others; they're twisted in interesting ways; the collectiveness of spiritomb, for example, or the uncommon darkness of phantump's origin, or rotom's poltergeist gimmick.
Only very few are free from any of those tropes, those being mismagius (witch), dusknoir (guide for the dead), golurk (golem), drifblim (a hot air balloon, and it's boring regardless; here's a case where the lack of the cliche is actually
worse for the pokemon).
For sure, there's a mix of common ghost concepts in there, as well as new ones. I think we differ on how important the "grudge" thing is in the design. I think it's secondary, with the core, most evident part of the design being the haunted sandcastle that drags things into it; similarly I think Banette's core design is a haunted doll or voodoo doll, with the grudge part being secondary. You say Sandygast's grudge is the "entire reason to exist", which I don't follow. It's the backstory, yes. What's a Squirtle's reason to exist? Most pokemon don't get backstories, or are assumed to have adapted to their environments, and that's enough for us. I think we can afford the same thing to ghost types - "a creature died and possessed this material, and now exhibits some properties of the material" doesn't seem any worse to me than "a creature lives in this environment, and adapted to reflect its environment."
The thing is, the pokemon is built on what you say about it; be it implied in its design and references, or directly on its description; each of those things is your choice as a designer, and has to be there for a purpose; design is communication, it sends a message, and in this case, I don't see a worthwhile message, it feels like they're trying to pretend there's a new message while sending snippets of old messages.
So if you say your pokemon was born from grudges,
that's what you want people to know, and it so happens that in this case it's a cliche, and without any clever twist, or something to keep it on the background. By including it in its description, the "why" of sandygast is something they wanted us to know (unlike most other pokemon), so everything goes from there; it can possess people/steal life (again, both cliches) because it is a ghost because it was born from grudges (another cliche). Leaving it blank and just talking about it as if it was any other creature, without saying where it comes, might have been better than using the cliche, and especially, doing it without any added value.
Fomantis/Lurantis arguably have nothing unique. They aren't the first mantis pokemon - that's Scyther - they're not the first pokemon to be fabulous - there's Lilligant, among others - and they're not the first pokemon to care about photosynthesis obviously. I still love them, and think it's fine if a pokemon combines already-used concepts. I just think you're being too hard on Sandygast, when it's doing the same thing, except that there hasn't already been a sandcastle pokemon.
They're a different type of mantis than scyther (after all, we have frillish and tentacool, or clydesdale and rapidash, among others) and they're unique in the sense they're mantis...es? without being bug-type; it's design isn't just fabulous, it stands out from the rest of grass types immediately; there's a clear message there. As I said, originality doesn't excuse a lazy execution, and their execution is lovely.
But I admit I may be biased in this one; as I said, I do often overlook flaws in pokemon. I'm just making an exception on sandygast and palossand because of how brazen and boring those flaws seem. People can like them, of course, but that doesn't make them richer, just popular.