Tribal hunt is essentially arena, except you get awarded a new weapon for every won battle. You have two allies to start with, and enemies come at you like in arena. There's also worm riders who toss dynamite out.
Okay, but what do you have to do to unlock it?
False edit: I decided to look it up... and I'm not 100% sure but someone said something about going training with people or hunting worms, but I don't remember this choice. If it's the one I'm thinking of I usually picked the one where youa ssault the castle, with the wooden spikes on either side and people shooting each other across the gap. I might try the other path just for fun. Once you unlock a gamemode on one profile as long as you don't delete that character it's unlocked for all profiles... I think.
Still relatively new to this game, but when do the shops unlock?
It happens partway through the story. There's a sort of extended tutorial of sorts where you're stuck in prison, and once you're released you get access to the 'hall' where all the weapons you've acquired are kept, along with a shop to buy new weapons and another shop to buy consumables and armor.
EDIT: I just discovered something sooooooooooooooooooooooooooo dumb. I stopped playing yesterday during the trial where you have to hit the ball as high as you can, and I come back to it today to find that it's permanently bugged. Time to restart my character =/
EDIT2: On the plus side I've learned how fun it is, when you're chained and have to dodge three guys, how fun it is to sit in the middle of them all and taunt them, then dodge out of the way at the last second. Two of them immediately exploded and the third was stunned for the rest of the level. I haven't gotten to steal one of their swords yet, they always explode to the sides where I can't reach them.
More: Hoooly crap, I just hit the Spawn so hard it literally popped off of the rock it was rooted to and was flailing around in the air before I put it out of its misery. I'm pretty sure it managed to fall off the level with a blood ruby but I did get an amethyst from it, and somehow I was hitting it in such a way that it spewed so many silver coins at me that the end game screen had stretched to try to fit all the coins on it. I should also note two things about Grim before I forget, first you can fill the blood gauge a little by cutting/bashing enemy bits that are already dead, and two you can hit the base of the Spawn for money after you've killed it.