Ok so instead of just walking around town showing people where the npc's are, Here's a Screenshot to make it easier to locate them.
There is a Legion Npc and a Clan Npc.
Legion Npc : Legion related quests. Hard quests which require the help of 2 or more players in a pt. They can be soloed if you're a good mace or gaunt. The rewards are good Exp, 50 vigor, and legion contribution. The legion contribution part is pretty much the reason why they are COMPULSARY. The level of the legion bosses and the map in which they can be located differ depending on your level. If you need help with legion bosses, Just PM me and I'll come help. If I'm not on, You can ask Kahlana, or Crypt. Mikhaila helps a lot too
. You can pretty much ask anyone in legion to help you, they'll come when they're free.
Clan Npc : This Npc gives you clan quests which are mainly just for increasing clan skills (Press Y clan skills can be found there). These quests are easy, and fast to complete. The reward will be EXP and Friendship Assembly Order. You NEED this item to do a group clan quest with your CLAN members (Not legion members, only clan). Contact your clan leader for more details on which clan quest to do and how to do it.
Ok So here's a Screenshot related to a clan quest which most people find difficult in completing. If you get a quest which tells you to find the weapon merchant's signboard, well here it is.