Confirmed If "Thalia, Guardian of Thraben" is "Ring-bearer", it will negate "Dress Down" and ask for 1 mana.

[reisyasu]

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reisyasu

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If "Thalia, Guardian of Thraben" is "Ring-bearer", it will negate "Dress Down" and ask for 1 mana.

 

[Firedrake]

A.) They'll need a game number, not your user name. Game number is 9 digits, starting with an 8.
B.) Did you pay the 3 mana required by Thalia to cast Dress Down?

 

[Neo001992]

Can confirm that if you make Thalia, Guardian of Thraben the Ring-bearer after Dress Down enters play that her static ability starts working again, and this is incorrect behavior.

https://imgur.com/a/vfBsLyU

Event#268910589 Game#878869538

 

[Firedrake]

A.) They'll need a game number, not your user name. Game number is 9 digits, starting with an 8.
B.) Did you pay the 3 mana required by Thalia to cast Dress Down?

OK, misunderstood the OP and order of play.