You need to use Lancet on the following fiends:
Jump
Damages one enemy
Is initially availible (you start the game with it)
Fire Breath
Fire damage to all enemies
Learn from: Dual Horn, Grendel, Valaha, Yenke Ronso
Seed Cannon
Non-elemental damage to single enemy
Learn from: Grat, Ragora, Sandragora
Self-Destruct
Sacrifice self (not KO, you disappear from battle) to deal extreme
amount of damage
Learn from: Bomb, Grenade, Puroboros, Biran Ronso
Thrust Kick
Non-elemental damage to single enemy, blow-away effect
Learn from: YKT-11, YKT-63, Biran Ronso
Stone Breath
Induces petrification status
Learn from: Basilisk, Anacondaur, Yenke Ronso
Aqua Breath
Water damage to all enemies
Learn from: Chimera, Chimera Brain, Chimerageist*, Yenke Ronso
Doom
Gradual death to a single enemy
Learn from: Ghost, Wraith, Biran Ronso
White Wind
Heals whole party 1/2 of Kimahri's current HP
Learn from: Spirit, Dark Flan, Yenke Ronso
Bad Breath
Inflicts random status abnormalities
Learn from: Malboro, Great Malboro
Mighty Guard
Casts Shell, Protect, and all Nul- spells on party
Learn from: Behemoth, Behemoth King, Biran Ronso
Nova
MAJOR damage to all enemies
Learn from: Omega Weapon, Nemesis*