EXP Stones are the items used to level Equipment. This is done so in the Forging Block by going into the Forge, selecting the piece of Equipment you wish to level, tapping 'Upgrade', and then tapping on the stones. Pressing down and holding on the stone will speed this process up immensely.
The primary source of these items is El Dorado whereby every map excluding bosses includes some stones as part of the loot table and the last 2 bosses include both EXP 2 and 3 as part of their loot. The first 2 pages only include EXP Stone 1s in their loot tables, however everything beyond them includes both 1 and 2, even if it is not shown to be so. EXP 1s drop far more often than 2, however the frequency improves the deeper you go. EXP Stone IVs are available as a reward from some Events.
|EXP Stone 1||100|
|EXP Stone 2||300|
|EXP Stone 3||1,000|
|EXP Stone 4||5,000|