Very interesting!!! I like the one time use abilities, especially that other factions will be able to see if you have them to use for the upcoming turn, which allows them to plan around them, which is a nice touch. The mutations mechanic as a whole seems very well thought out. The only concerning mutation is the woodland alliance mutation, which seems EXTREMELY strong, even without the ability to get it by just attacking a lone sympathy. Maybe change it to a free build or MORE FUN IDEA, be able to use it to get guerilla warfare if anyone attacks your mutant (defender gets higher roll), then it could act as an effective deterrent, as well as a strong ability for the one time use. The other mutations seem fairly balanced, with the potential exception of the Lord of the Hundreds mutation (maybe just one less hit in that battle instead of no hits) and the riverfolk one (I would make this a "draw two card and keep one", I think that is more balanced and thematic). It's unclear how you get general mutations. Can you get them in the same battle as when you get a faction specific mutation? Do you have to choose one mutation per battle? Are there four or eight total? Do they refresh as normal? (potential idea: maybe make general mutations only refresh when mutant dies and hatches again, idk) It seems like a good idea overall, so there isn't ever a clearing you don't want to battle in, as most clearings will probably have at least one token in them, even if it is just a general mutation. Last potential change to mutations: you can't use them in the same time that you gain them. If you attack the hundreds with a basic type mutation, then you can't use the hundreds mutation until the next turn.
It seems that this faction may struggle to recruit enough warriors, but perhaps this is intentional as the mutant is a powerhouse. I would like the necessary and thematic nerf to have the mutant lose all mutations when killed, I think it just makes sense, and then you can maybe make it a little easier to recruit, so its easier to defend your mutant.
The venomous spurs is overpowered. Pick two from these possible changes:
Make it more expensive - 2 cards for the ability, forces you to know when you want to use them
Make it only work on defense - Platypuses only use this for defensive purposes anyway
Make it weaker - You can only reroll ONE of the dice, not both
Make it more situational/add counterplay - It only works in battles WITHOUT the mutant
Finally, the generators. I think 8 might be just too many... I think limiting it to 6 in total would be a good change. However, with the current rate of recruiting, these might be eaten up on your backlines anyway, and might never even get close to 8 in total, so I don't know if this change is necessary.
Theme - lovely. Platypuses are weird and I like how matchup dependent it is, not because strength changes, but because your ENTIRE PLAYSTYLE needs to change based on opposing factions, which is great
Mechanics - well thought out and elegant. A few changes (some faction ones are overpowered, and the change so you can't use them the same turn you gain them). A little hard to figure out without a law of root, but I'm sure it is easy to understand with one
Sacrifice - Im going to be honest, not really there
Venomous spurs - overpowered
Recruiting - underpowered
All in all, a great, well thought out, unique faction idea. I'd love to see this in the game