How to report harassment

I'm not worried about the position in arena, more that he represents himself as another player and then relentlessly attacks said player.  Plus he purchased the account from a retired player, which I am assuming is against the TOS.  I would say creating a guild to specifically call me out would border on harassment.  So far he hasn't sent anything via game chat.

Finding his gg account is essentially impossible.  Just searching general guilds doesn't work because the guild list cuts off at around 40M GP and he was creating solo guilds.  He is currently guildless, so it is a matter of waiting until he actually joins a real guild to find him.  Searching for him specially is impossible because he has changed his name back to Mol Eliza and there are a ton of those.