SF is shortened for the term, Sorrow’s Furnace. Sorrow’s Furnace was a new
aream added in part of the September 7, 2005. Sorrow’s Furnace featured
a lot of new elements to the new area’s gameplay, including:

Seventeen new quests, most of them fully repeatable and offering high XP
rewards.
 
Four new cinematics.
 
A variety of new monsters, including new Stone Summit Dwarves that are the
strongest in the Shiverpeak Mountains, and entirely new types of creatures
that are being introduced to the game for the first time.
 
Boss monsters named after the contest winning entries.
 
Boss monsters in the new Sorrow’s Furnace regions drop newly-introduced green
“unique” weapons that are named after the boss.

To reach Sorrow’s Furnace, it is highly recommended you go to the Deldrimor
War Camp first. To get to the War Camp, go north from Camp Rankor to about
half way, and you’ll see an enterance for Grenth’s Footprints. Enter that
and just follow the signs leading to the War Camp.

To get to Sorrow’s Furnace from the War Camp, just go dead straight from when
you exit the War Camp and go down the mountain. The enternace will be right
there. Be prepared to encounter resistance!

EXAMPLE: Forming group for SF, invite yourself!