Permanent Super Strength
Have a Sovereign reach level 10 and put a point into Fire/Freeze/Shock Arms. When you now cast the spell on a member of your party it will temporarily raise their Strength by 3. Casting again will temporarily increase it by 3 again, but permanently increase by 3 as well. You can keep doing this until that party member has 999 Strength.
As you play through the game, you will find optional quests you can accept. Accepting some of them will grant you access to additional dungeons you wouldn't otherwise see. Find the dungeons indicated below by accepting the corresponding requests.
Animal Trail - Accept Monsters on the Animal Trail
Mountain Cleft - Accept Monsters at the Mountain Cleft
Ravine Fork - Accept Monsters at the Ravine Fork
Snowy Cavern - Accept Task at the Snowy Cavern