Outcast's Path

What about the elf castle? Why can't I enter through the garrison? Although the druid said I could go to the main one, the elves have a reputation of 70. And is the Dark Rune and the Tome of Dark Magic the same thing? I found the tome (the sphinx said), but where do I find the Dark Rune? I solved the elf castle issue by attacking it as part of the orc quest. And do I need to buy arrows for the centaur in the elf castle or in the workshop in front of the garrison? If I understand correctly, I just need to buy a cart with ammunition from them? Johnny was found, and everything worked out. I found the arrows and delivered them. I also managed to rob the place. I reached the point where I robbed the human treasury as part of the orc quest, and my reputation became 73 (but I still can't get to the main chieftain). Although I failed 3 orc quests (the ones given by the warlock before the main orc castle). Who will give the next quest after I rob the human treasury?