Monstructs doesn't have levels per se, but it progresses through Chapters. Each Chapter has it's own Mini and Main Bosses. some are cooler than others but all are challenging in their own way.(Changes may occur for sake of game balancing)
I'll display them by Chapter; Mini Boss first, then Main:
Chapter 1: The Journey Begins
Stranger
He attacks you with one random Monstruct. It might be weaker or stronger than yours so be on your guard.
Dayn
He uses a fairly well-balanced Team that could give you trouble if you're not strong enough.
Chapter 2: Clear Water, Thirsty Sand
Isis
She might not look like a threat but, she's got a lot of status ailment abilities to whittle down your Team's strength and can heal herself for the long haul.
Dessecado
You'll need to be fast or very durable to take on this guy. He has abilities that will soften just enough for a one hit KO!
Chapter 3: A Fungus Within
Treant
Watch out! This is one mean maple! It uses attacks that absorb your LP as well as AP
Funk-Gus
One of the more annoying bosses, it's accompanied by other mushrooms with abilities that can really be a pain to deal with!
Chapter 4: Menace of the Mines
Big BADger
This tenacious rodent doesn't know when to quit! not only is he hard to beat, but you'll have to fight him more than once. Hope you're prepared.
Chapter 5: Prisoners of the Past
Automaton Knight
Your basic beatdown machine. He has combos that can devastate in a few turns!
Bones the Jailer
Although he's nothing but bones, but his Skeleton Crew and abilities will put you in permanent lockdown!
Chapter 6: Lords of the Underground
Sara
She's cute, she's sassy and she has more power than you'd think. Don't take her lightly.
Claw
A mysterious master thief with a DEADLY secret. He can dish out damage with the best of them.
Chapter 7: Skyreach Mountain High
Goblin Chief
He brings the pain train, while his two bodyguards bring the buffs and backup.
Cirt
His Metal Caste Team is one of the most difficult you'll ever face. Have fun.
Chapter 8: Ferry Tale
Coro and Tapa
It's two, two, two jerks for one!
Vayn
Amazing how someone so beautiful can be so evil. Her Gem Team will beat you with style.
Chapter 9: Island InterErupted
Stranger
This time he comes back with a much bigger, stronger Team than when you first fought him.
Johl
Picture Hannibal Lechter with an attitude like Kaizer Souze. His Ember Caste Team is worse.
Just thought you'd like to see what you'll be crushed by in the game. MUWAHAHAHAHAH!!! XD
I'll display them by Chapter; Mini Boss first, then Main:
Chapter 1: The Journey Begins
Stranger
He attacks you with one random Monstruct. It might be weaker or stronger than yours so be on your guard.
Dayn
He uses a fairly well-balanced Team that could give you trouble if you're not strong enough.
Chapter 2: Clear Water, Thirsty Sand
Isis
She might not look like a threat but, she's got a lot of status ailment abilities to whittle down your Team's strength and can heal herself for the long haul.
Dessecado
You'll need to be fast or very durable to take on this guy. He has abilities that will soften just enough for a one hit KO!
Chapter 3: A Fungus Within
Treant
Watch out! This is one mean maple! It uses attacks that absorb your LP as well as AP
Funk-Gus
One of the more annoying bosses, it's accompanied by other mushrooms with abilities that can really be a pain to deal with!
Chapter 4: Menace of the Mines
Big BADger
This tenacious rodent doesn't know when to quit! not only is he hard to beat, but you'll have to fight him more than once. Hope you're prepared.
Chapter 5: Prisoners of the Past
Automaton Knight
Your basic beatdown machine. He has combos that can devastate in a few turns!
Bones the Jailer
Although he's nothing but bones, but his Skeleton Crew and abilities will put you in permanent lockdown!
Chapter 6: Lords of the Underground
Sara
She's cute, she's sassy and she has more power than you'd think. Don't take her lightly.
Claw
A mysterious master thief with a DEADLY secret. He can dish out damage with the best of them.
Chapter 7: Skyreach Mountain High
Goblin Chief
He brings the pain train, while his two bodyguards bring the buffs and backup.
Cirt
His Metal Caste Team is one of the most difficult you'll ever face. Have fun.
Chapter 8: Ferry Tale
Coro and Tapa
It's two, two, two jerks for one!
Vayn
Amazing how someone so beautiful can be so evil. Her Gem Team will beat you with style.
Chapter 9: Island InterErupted
Stranger
This time he comes back with a much bigger, stronger Team than when you first fought him.
Johl
Picture Hannibal Lechter with an attitude like Kaizer Souze. His Ember Caste Team is worse.
Just thought you'd like to see what you'll be crushed by in the game. MUWAHAHAHAHAH!!! XD