When playing Showstopper on Sett, can you immediately spend the buff given before Sett moves to the battleground?

Question

Accepted Answer

Ruling: No, you cannot immediately spend the buff from Showstopper before Sett moves to the battleground. Sett's ability is base speed, and once Sett moves to the battlefield the game is in showdown state.

Sequence:
- Showstopper gives the buff
- Sett moves to the battlefield
- Game enters showdown state
- Sett's base speed ability cannot be used during showdown

Nuances:
- Everything in the game is base speed unless it specifically says Action or Reaction