Find the "Zodiac Spear"
The ̶0;Zodiac Spear̶1; is a unique item with a very high attack rating and is the most powerful weapon that can be found in the game. However, to find the item, the player must not open four specific ̶0;forbidden treasure̶1; chests during the course of the game. The first chest is located in Rabanastre. It is in the Lowtown area, next to the door to Old Dalan̵7;s place. The second chest is found at the Rabanastre Royal Palace, in the southeastern corner of the cellar. The third chest is found in the Nalbina Dungeons at southern end of the Confiscatory. The final chest is on the shore of the Phon Coast, at the top of the Vaddu Strand, where there are 16 chests laid out on the beach. Leave all of the chests alone to avoid opening the forbidden chest.
Find the "Matamune"
You̵7;ll need to collect five differently colored bottles that appear while fishing and bring them to specific locations to retrieve the location of the King of Nebra. The bottles are collected randomly during fishing at any location. The ̶0;Blue Bottle̶1; must be brought to the sunken boat in the Nabreus Deadlands. The ̶0;Green Bottle̶1; must be brought to the small hut in the Salikawood. The ̶0;Red Bottle̶1; must be brought to the northwest corner of the Babbling Vale in the Mosphoran Highwaste. The ̶0;Yellow Bottle̶1; must be brought to the windmills in the Cerobi Steppe, and windmills one, two, five, seven and nine all need to be on, and the other windmills must be switched off. The final bottle is the ̶0;Black Bottle,̶1; which must be brought to the Sluice Gate in the Garamsythe Waterway, at the south end of the room. After collecting the location letters from all five bottles, walk into the West Annex of the underground Barheim Passage via the Zeviah Span, then turn back into the Zeviah Span, but walk slightly north of the main path as you enter the Zeviah Span. You̵7;ll now be in a small corner of the bridge that is surrounded by rubble. Walk to the end of the section for a cut-scene, and after the scene ends you will be given the ̶0;Matamune.̶1;
The King of Nebra
̶0;The King of Nebra̶1; is the final, legendary fish that can be caught while doing the fishing side-quest. The quest for the King of Nebra can only be started if Gilgamesh has been defeated in the ̶0;Battle on the Big Bridge Clan Hunt̶1; side-quest and if the ̶0;Matamune̶1; fishing rod has been received. Head to the Upstream area of Ruksel and fish until you find the ̶0;Cactoid Compact,̶1; which enables you to enter the Hidden Shoals. Enter the Hidden Shoals and fish there until you find the ̶0;Cactoid Commendation,̶1; which allows you to enter the ̶0;Den of the River Lord.̶1; Fish here and you will finally find the King of Nebra.
Mark Hunting and Rare Monsters
Mark hunting is a side-quest that is available early in the game and is first given in Rabanastre. Petitions to hunt marks can be accepted independent of the main quest and completing hunts raise the overall clan ranking. There are 45 marks in all ̵1; some who are more powerful than the final boss of the game. GameFAQs has a list of all the marks and their respective locations. There are also 80 rare monsters that can be killed in the game ̵1; these monsters must be found at very specific locations and times and often give the party rare or valuable loot. GameFAQs has both a rare monster hunting guide and several maps that show the location and time for each rare monster.