Access first to Blue Dragon Cave. Have your characters raise their level up to 52-55 (as Hiro learned Triple Sword and Lemina learned Power Drive). Now go back to White Dragon Cave. And FIND a Chiro Mongrel/s. Lemina should equip two Chiro Crest (you can steal it from a Chiro Mongrel, gives her the abilities to attack first) and have her cast Power Drive with Hiro. Hiro should use Triple Sword, Jean should use her Blue Dragon Palm , and equip Ronfar with Earth and Thunder Crest or two Thunder Crest and do the trick ^-^. I suggest you equip both Hiro and Jean with two Warrior Crest (you can buy the Crest in Horam). This should at least kill one Chiro Mongrel at 40% rate.
Note: Have Leo joins party. And have him equip with two Warrior Crest. Have him use Grizzly Blade or Flash Blade (but I used a normal attack instead of the Flash Blade or Grizzly Blade). The rate will be at 47%.
Go back to Vane(while in the epilogue) and go to the magic guild manor where borgan and miria is.Walk up to the curtain above them and push O, X, O, X,O until you here a chime then check you inventory.
When you are at the White Dragon Cave there is this monster that gives 33333 exp and 11111 silver if you kill it.The name is chiro mongrel(not shiro), it has resistance against everything and has 900-1000 life.It's recommended that you come here after you beat zophar and in the epilogue.The ez way to kill him is to:
Jean-blue dragon wave
ronfar-i had him attack since he had no magic with high damage
Note:this is the not only way or the best, but this is the way i did it( i couldnt kill one til lvl 56 and in the epiligue)