As of 1 January 2017, here's a list of monsters that can appear in normal battles:
Any level
- Orb fountain
- Lost soul
- Anniversary dwarf
- Anniversary gnome
Around level 0+
- Bee
- Black bones
- Blue poring
- Cow
- Ding bats
- Dirt Eater
- Enchanted bones
- Ironshell
- Orcish impaler
- Poring
- River crab
- Rock lizard
- Stone Eater
- Wild rabbit
- Yagudo zealot
Around level 10+
- Air elemental
- Bark spider
- Beetle
- Bloodgoyle
- Blue slime
- Bone soldier
- Cactuar
- Citadel bats
- Coiled snake
- Combat
- Copper beetle
- Creeper
- Cursed bishop
- Cursed pawn
- Cursed rook
- Cyberman
- Dalek
- Dark elemental
- Dark knight
- Dark octopus
- Devil manta
- Dragoon ghost
- Earth elemental
- Female vampire
- Fire elemental
- Forest giant
- Gekko
- Gekko dwarf
- Ghost turkey
- Gibdo
- Goblin enchanter
- Goblin shaman
- Goblin smithy
- Green slime
- Healslime
- Heraldic imp
- Ice elemental
- Light elemental
- Mad piranha
- Mad cow
- Male vampire
- Mammoth
- Maniac
- Metal slime
- Minotaur
- Moblin
- Nightmare hornet
- Nightmare vanguard
- Ninja assassin
- Poison slime
- Pride demon
- Red slime
- Retro hippie
- Roaming sapling
- Ruby quadav
- Sabertooth tiger
- Samurai ghost
- Shrapnel
- Small werewolf
- Snow giant
- Snow lizard
- Snow wight
- Starman junior
- Strolling sapling
- Stygian
- Thunder elemental
- Treant
- Undead black mage
- Undead corsair
- Undead dragoon
- Undead knight
- Undead monk
- Undead ranger
- Undead red mage
- Undead samurai
- Volcano wasp
- Water elemental
- Wooden puppet
- Wyvern
- Yagudo oracle
- Yagudo scribe
- Young mummy
- Zarklet
- Zombie
- Zombie chef
- Zombie salesman
Around level 50+
- Acrobat
- Bigclaw
- Blue Medusa head
- Brook Sahagin
- Chimyriad
- Count
- Countess
- Creek Sahagin
- Cursed queen
- Dark mummy
- Decapiclops
- Deku scrub
- Demon knight
- Demon samurai
- Demon warrior
- Demon wizard
- Dhalmel
- Elder treant
- Football zombie
- Ghost bomb
- Gnole
- Goblin berserker
- Gremlin
- Large cow
- Orcish gunshooter
- Orcish neckchopper
- Orcish predator
- Oxocutioner
- Pugil
- Redead knight
- Sapphire quadav
- Scarab beetle
- Shark
- Small armos
- Stag beetle
- Starman deluxe
- Stream Sahagin
- Succubus
- Yagudo conductor
- Yagudo herald
- Zombie rock star
Around level 100+
- Baelfyr
- Balrog
- Bear shark
- Bee bear
- Butcher
- Byrgen
- Cave tiger
- Crimson slime
- Crimson zombie
- Cucco
- Drachenlizard
- Emerald quadav
- Geyfyrst
- Ghost samurai
- Gray werewolf
- Healing slime
- Highland treant
- Infernal bovine
- Kindred knight
- Kindred samurai
- Kindred warrior
- Kindred wizard
- Maneating hornet
- Midnight slime
- Mosquito
- Mountain worm
- Mud pugil
- Orcish wyrmbrander
- Ore Eater
- Revenant
- Rock Eater
- Ruly imp
- Sand digger
- Sandy claws
- Shopkeeper
- Silver Medusa head
- Starman ghost
- Ugly knight
- Ungeweder
- Yagudo prior
- Zu
Around level 200+
- Bathos
- Blue bones
- Chaos idol
- Cureslime
- Cursed mummy
- Death knight
- Desert beetle
- Ermit imp
- Final starman
- Flame knight
- Frost knight
- Gold Medusa head
- Goliath beetle
- Greater pugil
- Green bones
- Guardian treant
- Hikari reaper
- Icefang tiger
- Large armos
- Magic pot
- Magnes quadav
- Medium armos
- Mineral Eater
- Moonfang
- Pathos
- Purple bones
- Ravager
- Reaver
- Red bones
- Sea pugil
- Unicorn
- Veteran quadav
- Yagudo prioress
- Yagudo summoner
Around level 500+
- Ancient mummy
- Elder count
- Elder countess
- Fission metroid
- Metroid
- Sierra tiger
- Space Pirate
- Space Pirate Aerotrooper
- Treant sapling
- White werewolf
Around level 1000+
- Death Armos
Around level 1500+
- Alpha werewolf
- Archdemon knight
- Archdemon samurai
- Archdemon warrior
- Archdemon wizard