The Eidolon search sidequest is a mobile version exclusive sidequest in Final Fantasy IV and is the only way to obtain the Piercing Magic augment in these versions. The player must talk to the eidolon in the Feymarch, who resides in the building west of the Inn who will ask Rydia to fetch his eight missing friends who have gone missing during their trips.
Eight eidolons, who wear the standard red hooded cloak, are found within specific locations in the three world maps: Overworld, Underworld, and the Red Moon. They can be found in towns, caves, mountains, and other specific places. If spoken to, the eidolon will provide a clue, and the clue will switch to the next when the player fetches the friend he mentioned. The eidolons fetched will be seen gathered in the house to help the player keep track of the number. If the player returns to the house with all eight eidolons, he will be rewarded with the Piercing Magic augment.
|Kaipo||The first friend the eidolon will mention is in Kaipo, and is drinking the oasis water "like crazy". He is around the place where the Item Lore augment is obtained.|
|Mount Ordeals||The second friend is in Mount Ordeals, as the eidolon mentions one wanted to get a "great view". He is in the corner near the save point.|
|Dwarven Castle||The third friend is in the Lali-Ho Pub in Dwarven Castle, drunk with Dwarven Brew. He is sitting on the table on the right corner.|
|Sylph Cave||The fourth is inside the Sylph home (the second floor) in the Sylph Cave, and is talking to a Sylph.|
|Kokkol's Forge||The fifth is found in the entrance of Kokkol's Forge, and had a sword made.|
|Hummingway Home||The sixth is found inside the Hummingway Abode, unable to get the melody out of his head even when he goes back to the Feymarch.|
|Lair of the Father||The seventh friend is "well-behaved" and "on a Lunar expedition", as the eidolon mentions. He is found near Bahamut's hall in Lair of the Father, on the right side before the stairs. He asks Rydia if she is paying her respects, then the eidolon returns home to the Feymarch.|
|Troia's Chocobo Village||The last one is found in Troia's Chocobo Village. The eighth is found near a white chocobo, and he has been flying on the black chocobo.|
|Passage of the Eidolons||Though not counted, if the player has talked to the eidolon in the Feymarch, an eidolon will appear at the entrance of the Passage of the Eidolons, asking if the player wants to come with him to town. He exists so that the player will not have to go through the dungeon floors again and again. This saves time and allows the player to arrive at the eidolon's house easily, where progress can be tracked and clues be given.|