It's a fantasy role-playing game.

DM: You are Jester Lavorre, a tiefling cleric . You are the member of the famous group of adventurers. Previously, Yasha has a tinder box, so Nott uses Mage Hand to hold the dynamite, Yasha lights it, and Nott and you (who has cast Pass Without a Trace and needs to be within 30 feet) sneak up and move it into the house. After a tense pause, it explodes, blowing apart the tree and knocking the troll prone, and allowing the party a surprise round.
DM: Okay, you are readying an attack, for what? What's the trigger? Comes within range? Got it. Okay, that finishes Yasha's turn. Jester, you're up.
Player: That's me! I'm going to cast Spiritual Weapon right above it!
DM: Right above it!
Player: And it's going to hit him!
DM: All right, roll for your attack.
Player: It's not at disadvantage, because it's melee, right?
DM: Correct. Technically it's at advantage, because it is prone. I imagine it's considered a melee attack.
