The beginning of GvG?

So as a lot of us already know, the maps from Random Arenas and Team Arenas are the old arenas that used to be found around Tyria, before Factions. Then, of course, there is Hero's Ascent, which used to be in the Tomb of the Primeval Kings, before Factions. But Guild vs. Guild battles take place in guild halls, and guild halls only exist in the battle isles (ie. under Canthan authority). Moreover, to get a guild hall, you have to beat the Canthan HA, and take the sigil to a Canthan ambassador. So what I'm curious to know is how did GvG exist/work before factions, or did it at all?

The guild hall ambassador was, I believe, Krytan. I think the lore behind it was that Ascalon had forbidden any guild save the King's to hold any land in the kingdom, to put an end to the Guild Wars (hence why you can't buy a guild hall in pre-searing). Once you got to LA, you could supposedly buy a guild hall way out to sea.

i'm fairly certain that there are guild hall ambassadors in lions arch as well as the battle isles themselves...nothing to do with cantha or factions, gvg's been around since the beginning

All PvP was taken to the battle isles when the Tomb of the Primeval Kings became an unstable connection to the underworld and overrun by mobs. The Zaishen volunteered to host it on their islands where they could protect people from the mobs of the underworld. HA is merely a secondary access point to the hall of heros, it does not make the hall of heros canthan. Besides, u can access the guild ambassador in LA to go and buy a sigil without ever setting foot in cantha or HA.

I somewhat remember the Guild Halls were always bought from the Canthan Ambassador (lore-wise), hence the design of the Guild Lord. Pre-Battle Isles the hall location icon was just out to sea on the world map.

Cantha was already conceptualized before Factions.