Unique - Maim: Champion kills, assists and large monsters slain will grant Feral stacks. Basic attacks deal 25 (+1 per Feral stack) bonus magic damage and restore 10 health. Minions and monsters take triple the bonus magic damage. Unique: Gain 30% increased gold from monsters Unique - Gold Income: You may only be in possession of 1 Gold Income item.
Maim's bonus damage does not take into account any kills, assists or large monsters slain prior to obtaining Feral Flare - i.e. the bonus damage will always begin at 75. 
The name "Feral Flare" is possibly derived from "FeralPony" (Riot game designer). The Feral stack buff's tooltip also alludes to this.
However note that "feral" is also a synonym to "wild", thus Feral Flare could simply be a reference to both the jungle and jungling.
During the Season 4 Preseason, this item's passive was originally going to be given to a remade Madred's Bloodrazor.
For comparison, Feral Flare's magic damage equal to 4% of the target's maximum health against champions with 625 (+25 per Feral Stack) health. For example: at 95 kills/assists/large monsters slain you will be doing 120 bonus magic damage to champions (4% of a target with 3000 health).
Trick2g has the fastest known completion of the Feral Flare in Ranked Solo/Duo with a time of 10:26.
Builds from Wriggle's Lantern upon killing 25 large monsters. Stats: 15 attack damage and 35% attack speed.
Retains the 30% bonus gold passive.
Unique Passive - Maim: Champion kills, assists and large monsters slain will grant Feral stacks. Basic attacks deal 100 (+3 per Feral stack) bonus magic damage and restore 10 (+1 per Feral stack) health. Enemy champions take 33% of the bonus magic damage.