If I have Miss Fortune Buccaneer out and then play Yone to an open battlefield does his Weaponmaster trigger before or after his Conquer ability to deal damage equal to his Might to an enemy unit at base?

When you play Yone, Blademaster to an open battlefield using Miss Fortune, Buccaneer's ability, his Weaponmaster ability will trigger and resolve before his conquer ability.

Here is the breakdown of the sequence:

1. Playing the Unit: You play Yone to the battlefield. Because he has the Weaponmaster keyword, this creates a "When you play me" triggered ability.
2. Weaponmaster Trigger: Yone's Weaponmaster ability is placed on the chain. You resolve this ability, allowing you to choose an Equipment and attach it to Yone at a discounted cost.
3. Conquer Trigger: Yone's conquer ability ("When I conquer a battlefield that was uncontrolled...") is a triggered ability that only triggers after the battlefield has been successfully conquered.
   • Playing Yone to an open battlefield initiates a showdown.
   • The showdown must resolve (and you must successfully conquer the battlefield) before the conquer trigger can even be placed on the chain.

Summary of Timing:

• Weaponmaster triggers as part of the process of playing the unit (it is a "When you play me" effect).
• Conquer triggers only after the showdown concludes and the battlefield is officially conquered.

Therefore, the Weaponmaster effect happens immediately upon Yone entering play, while the conquer effect happens much later, after the combat resolution.