The exact requirements for basic elemental avatar HTBs:
1. Beat all 6 basic elemental avatars standard Trials. Minifork versions don't work for anything besides unlocking pacts IIRC.
2. Use up all whispers to gain a standard reward. Has to be something from the reward list. Pact works, gil works, etc. Consuming them for ring or Fenrir does not count. You do not have to accept the pacts or even have SMN unlocked.
3. You should be able to buy the "Avatar Phantom Gem" as soon as you have spent all 6x whispers.
For the Feared One:
1. Might need to complete COP missions. Would not be surprised at all if you hit some sort of hidden lockout flag like what's common with ROV missions.
2. Silly question, but did you verify that the character had at least 15 merits to buy the KI at the time you checked the npc? And that you don't have the KI in possession already? It's "Feared One Phantom Gem" under Temporary Key Items.
Thank you for making it very clear how to do the Avatar fight^^
... and silly question was not so silly. I found phantom gem ki ... /facepalm. Was checking the perma Ki yesterday i guess. Seems my husband has bought them all once when he passed by the npc with our mule ><;
But aleast now i know what i need to do to fight the avatars with mule ... so not a total pointless thread ^^;
thx everyone for the replies.