My opponent has Hero's Blade on the battlefield. He plays Yisan, the Wanderer Bard and attempts to attach Hero's Blade to it. In response, I cast Lightning Bolt and attempt to deal Yisan 3 damage and kill it before Hero's Blade is able to attach. My question is, am I able to do this? Can I cast Lightning Bolt so that its effect will resolve AFTER Yisan enters the battlefield but BEFORE Hero's Blade is able to be attached?
Yes, you can. Hero's Blade's ability triggers "Whenever a legendary creature enters the battlefield under your control," which means that the order of events goes like this:
- Your opponent casts Yisan
- Yisan finishes resolving and enters the battlefield. This causes the Hero's Blade's ability to go on the stack. At this point, Yisan is on the battlefield
- You respond to the triggered ability with your Lightning Bolt.
- The Lightning Bolt resolves, and kills Yisan.
- The triggered ability resolves, and does nothing.
As a side note, the Equip ability can only be activated "whenever you could cast a sorcery," so your opponent would not be able to Equip the Hero's Blade in response to your Lightning Bolt.