Can you react with Shakedown before Sett Brawler gets buffed by Sett Legend's power, preventing him from being saved?

Ruling: Yes, you can react with Shakedown before Sett Brawler gets buffed. Sett's ability is a WYPM (When You Play Me) trigger that goes on the chain, and Shakedown is at reaction speed, so you can respond to it before it resolves.

Sequence:

• Sett Brawler is played, triggering the WYPM ability
• The buff ability goes on the chain
• Before it resolves, you can react with Shakedown at reaction speed
• Shakedown resolves first, removing Sett before the buff can save him

Nuances:

• When Sett's Legend power spends the buff to give +4, the buff falls off as a cost. While the +4 ability is on the chain, Sett would be 4M (not 5M anymore), making him vulnerable to effects like Stupefy or Gust during that window.