For Meryl, you have to go to the Giant Legion Hive.

Dryu
-Talk to Joen at San Tovance WITH Meryl in the party then go to the Impact Legion Hive.

Chiquitita
-Talk to the Elder in Cantore Village
-Go to the Ghost Legion Hive

Graham
-Talk to one of the soldiers at Larcyle Fort. He's just below the stairs if you use the Warp Gate to Larcyle Fort.
-Go to the Orc Legion Hive

Mariel
-Talk to Chaos at Hyatt
-Go to the Flame Legion Hive

Baron & Rhinos
-Talk to Liebenhein at Quincine
-Go to the Vampire Legion Hive

Adam
-Talk to Rebecca at HQ
-Go to the Golem Legion Hive

I have done the Ordeal for Klein and Freyja but I forgot their location.