/dialogue: Opens an NPC's dialogue for a player, or switches which dialogue scene an NPC shows.
Syntax
<angle brackets> are required, [square brackets] optional. /dialogue has 2 forms:
/dialogue <open: dialogueopenaction> <npc: selection> <player: selection> [sceneName: id]
/dialogue <change: dialoguechangeaction> <npc: selection> <sceneName: id> [players: selection]