The Few, the Proud, the Brave
1) This infintely repeatable quest, which can be done from level 15, starts with Vice Hierarch Perwan in the Cave of Souls west of the Kamael Village, where you started your career as a fighter. This quest doesn't give additional rewards but it is one of the quests the Newbie Guide gives you a huge boost in exp/sp for doing.
2) Perwan says, not quite correctly, that people have been attacked by Crimson Spiders while on their way from the Village to Nornil's Cave. He asks you to help with exterminating the monsters and bring back as a proof Crimson Spider Claws.
3) The Crimson Spiders are actually not in Mimir's Forest but east of Nornil's Cave, where there is a marker on your map.
Be careful. The - unpoisonous - spiders are absolutely passive, not even helping their own kind, but they are intermixed with highly aggressive Muertos Warriors (lvl 14) as well as passive but social Muertos Lieutenants (lvl 17). Since you have to kill those in self-defence anyway, you might as well pick up the "Muertos Feather" quest from Grocery Trader Trevor to make some additional adena.
4) You can kill as many spiders as you like (the quest item acquisition rate is about 1 out of 4), but since there is a bonus of 2187a if you bring in 10 or more Crimson Spider Claws, you can maximize your income by returning to Perwan as soon as you have 10 Claws. The base reward is 45a/Claw.
As mentioned above, this quest is infinitely repeatable.