Wild Arms 3

Migrant level is raised through finding migrant seals which are usually found in treasure chests. You can get this relatively early in the game (around 10-20 hours in). Most migrant seals are acquired via duplicator doors. Those are the brown/redish doors you can sometimes find in dungeons. Open your inventory screen and use a duplicator while standing in front of them and it'll open. Inside is usually treasure chests that sometimes contain a migrant seal. You'll need 4 in total for this trophy.