You Get A Hotspot Towards The End Of Chapter 4 To Clear The Thunder Plains To Make Them Safe For The Impending Concert.
Follow The Map Marker To The Newly Opened Cave And Clear Through It To The Back.
Zalamander's Sitting In The Back, WIthout A Save Point Between You And Him. Be Careful, The Monsters Here Are No Joke!
Zalamander
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7,120 HP
Not Immune To Defense, Attack, Magic, And Mental Break.
If You Cant Smack Him Down, Heal A Bit And Switch To Some Special Dresspheres To Chunk Him Down.
Achievement Pops When You Beat Him.
Side Note*
Once You Beat Him, You Must Walk Back Out Of The Cave Before You Get Mission Complete.
Good Luck!