F-soul can only be obtained on an item (weapon or armour etc) by the following method;
1. You must find (not buy) a STANDARD elite item.
2. You must USE the item for a long period of time on your character... how long exactly I'm not usre but all tests conducted have been over a few week period.
3. You must 2 socket the item yourself FIRST
4. You must +12 the item yourself SECOND
5. LASTLY you must super the item yourself
At this point you "should" but not always get F-soul on your item.
The rumors about what F-soul will do (from what I've heard about it) are as follows, keeping in mind all or some of these may or may not be true.
1. One hit kill proc... the ability to be able to 1 hit kill anyone in the game, regardless of potency. Chance based attack (kind of like quad chop and similar attacks). This rumor is supposed to affect weapon based f-soul only
2. Invunerability... to get hit for 0 damage by anyone in the game regardless of potency. Chance based similar to the 1 hit attack, but this is supposed to be for armour
3. Automatic Healing and Mana Recharge (maybe stamina as well?)... as it suggests you can heal automaticcaly etc. this one is supposed to be the effect of necklace and/or braclet
4. Special effects... like dragons flying around you and big glowy wank-factor special whizzy effects flying out of you as you attack people. All f-soul items are rumored to give some kind of special effects based on the type of gem(s) socketed into the item.
by kSharp