How do Soak/Trick or Treat/Forest's Curse work against a Terastallized Pokemon?

Question

I have three questions about terastal and soak/forest's curse/trick or treat: 1.if a pokémon is under the effects of forest's curse and terastalizes will the effects of forest's curse stop 2. Can you use forest's curse on a terastalized pokémon 3. Will either work as well for soak/trick-or-treat?

Comments

I'm pretty sure someone already asked a question about 2 and 3 but I can't find it

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Does this answer your question? https://pokemondb.net/pokebase/413220/how-does-terastallizing-interact-with-type-changes

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Terastalizing blocks the type loss from Burn Up and Double Shock, as well as ignoring Protean and Libero abilities that normally change the type of the user based on move usage.  I imagine that moves like Forest's Curse, Soak, and Trick-or-Treat would all fail, based on this information.

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Thank you sumwun that helps answer my question:)

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What questions do you still have?

Answer 1

If a Pokemon is under the effect of forest's curse and terestralises, the effect doesn't stop. The Pokemon becomes the tera type + grass.

You can't use forest's curse on a terestralised Pokemon. Terestralised Pokemon cannot have their type changed.

It should work the same for soak/trick or treat since they're the same move but with a different type.

I tested it in these replays, I hope it answers your questions completely.

https://replay.pokemonshowdown.com/gen9customgame-1806196050

https://replay.pokemonshowdown.com/gen9customgame-1806197234

Answer 2

Soak, Forest's Curse, and Trick-or-Treat always fail when used on a Pokemon that is already terastalized.

A Pokemon under the effects of Forest's Curse/Trick-or-Treat always loses the effects upon terastalizing.

When a Pokemon hit by Soak terastalizes, it retains the STAB properties from the water type regardless. If a Pokemon hit by Soak terastalizes into the Stellar type, it will retain the water typing. These properties remain until the Pokemon is switched out.

(Note that for this I didn't test Trick-or-Treat but I'm assuming it works the same as Forest's Curse.)
Source: Testing in the game but I tested on Showdown and got the same results.

Comments

If a Pokemon has its type changed by soak or some other effect, doesn't it still keep the new STAB after Terastalizing?

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In regards to the moves OP asked about, only Soak does. Based on the results I got with these moves, I'm guessing that moves that change the target into another type like Soak do retain STAB but moves that add a type like Forest's Curse don't. However, I haven't done testing with all the type changing moves since the original question didn't ask for that.