While hunting in certain zones, you can encounter the Lucky Pig. (It has replaced the Fortune Bug.) Lucky Pig is a flying pig with white feathery wings. When it appears, it shouts and approaches a nearby character at random.
Lucky Pig eats Adena dropped nearby and disappears if not fed for 10 minutes. You can feed Adena to Lucky Pig a minimum of three times and a maximum of ten times. Talk to it to determine if it's full. When it is full, Lucky Pig loses its wings. At that point, it may give you a reward for feeding it.
You can obtain a reward either by feeding Lucky Pig ten times or talking to it after you have fed it at least three times.
Lucky Pig Locations:
Level 52 Lucky Pig: Enchanted Valley.
Level 70 Lucky Pig: Forest of the Dead, Valley of Saints.
Level 80 Lucky Pig: Wild Beast Pastures, Plains of the Lizardmen, Sel Mahum Training Grounds, Fields of Whispers & Silence, Crypts of Disgrace, Den of Evil, Primeval Isle, and the solo area in Dragon Valley.
Lucky Pig Rewards:
Level 52 Lucky Pig: Neolithic Crystal B and Top-Grade Life Stone - Level 52.
Level 70 Lucky Pig: Neolithic Crystal A and Soul Crystals - Stage 11.
Level 80 Lucky Pig: Neolithic Crystal S and Attribute crystals.
You can exchange Neolithic Crystals with a Dimensional Merchant to change a normal weapon into a rare weapon. (Dimensional Merchants are now functional.) To change a weapon into a rare weapon, you need to supply the Dimensional Merchant with the weapon and 1 Neolithic Crystal of the same grade.
Source - http://legacy.lineage2.com/news/highfive_04.html