From Guild Wars Wiki
Arena guards are NPCs found in towns who, when spoken to, will teleport a character to an arena where you can compete in PvP battles. These NPCs are recognized by the "[Arena Guard]" tags in their names.
 List of NPCs
- Bobby → Costume Brawl (outpost)
- Captain Li Sah → Dragon Arena (outpost)
- Rollerbeetle Trainer → Rollerbeetle Racing (outpost)
- Wintersday Priest → Dwayna Vs Grenth (outpost), Great Temple of Balthazar, Lion's Arch, Droknar's Forge, or Kamadan, Jewel of Istan