While the idea itself is fairly solid, I think the problem with implementing this with a token is that unlike tarstuffs, serpents are very much alike, which would make the token very niche.
Alternative suggestions:
1. "
Change monster X to Y"
command - would change all monsters of type X to monsters of type Y. Proposed edge case resolution:
1.1. Turning a multi-piece monster (serpents, gentryii, giants) to a single-piece monster (everything else) would replace every piece of the multi-piece monster. So "
Change monster Serpent to Roach"
would replace a 4-tile long serpent with 4 roaches.
1.2. Turning a single-piece monster to a multi-piece monster would do nothing with the exception of Gentryii.
1.3. Turning a rock giant into any other multi-piece monster would do nothing.
1.4. Turning a serpent into a gentryii would work, but not the other way
2. "
Swap monster X with Y"
command - would swap monster types.
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