Rune Monsters are really tough monsters, stronger than the rest of the monsters in their area. Some of them have a chance to drop rare weapons or armor, while the stronger ones tend to drop nothing. Eventually there is an NPC who you can talk to and track your progress with killing the Rune Bosses for each Chapter. They are divided by spawn location because you unlock various new regions in each chapter. Generally, they tend to remain within the newly unlocked region although outliers appearing in past or future regions do exist.
Rune Bosses Per Chapter (And How/Where To Spawn Them)
Ow My Face appears in Witch Forest south of Cool Farm. There is a sign in a clearing that says "Warning: Bees" and the boss rune will appear in front of that sign. Kill multiple Death Hornets in Witch Forest to cause it to spawn. Drops the Bees' Knees (Loki-specific armor) upon death. This boss is farmable and spawns indefinitely.
Greater Earth Sprite appears in Witch Forest east of the Stu. There is an empty clearing in the center of a loop. This clearing in particular has no decorations like rocks or trees in it, but Broh-lers will spawn there. The Earth Sprites needed to kill to spawn it appear in the loop around the clearing. Has a specific rare loot drop but I don't remember it. Farmable as it appears indefinitely.
Archon appears in Witch Forest to the southeast of the Stu, in a clearing with a rock and six dead trees. The regular Archon enemies spawn between the dead trees but not outside them, so to spawn the Archon boss's rune, one must walk between the trees a lot. This boss has a rare loot drop, Golden Sword I believe, but its regular loot drops are more appealing early-game as it can drop Immortal souls. This means a LOT of free mana healing and you'll be able to stock up on them very early on in the game. Farmable as it appears indefinitely.
Jason can be spawned by fighting thirteen Fridays. If you mess up, this number restarts upon reentering the region. Zubat spray, Stealth Cleaning, or Moonwalk is recommended to avoid unwanted battles. This boss spawns in the left part of the region, as North Witch Forest is one big loop with a "/" through the middle. Can drop Jason's Mask, a unique helm type of armor. Farmable; appears indefinitely.
True Sunday can be spawned by fighting each day of the week Sunday-Saturday once. If you mess up, this counter resets upon reentering North Witch Forest. Moonwalk is recommended to escape unwanted battles with the wrong day. This boss spawns in the middle "/" part of the region, as North Witch Forest is one big loop with a forwardslash through the middle. I don't remember if this drops any unique items. Probably not. Farmable; appears indefinitely.
The Bright Fairy, a UPN Pass Rune Boss, can be spawned by killing Light Pixies along the path south-southeast of the Stu, between him and UPN HQ. The Rune itself will spawn on the same row as the middle path and should be visible from where you are farming Light Pixies. It drops the Golden Staff as a rare loot drop but aside from that, it usually drops 1-3 light shards. If you are farming to give Kuno Divine Light early game, this is an enemy you should expect to fight 7-10 times. Farmable; appears indefinitely.
The Blazing Black Dragon spawns in UPN Pass after several Mossy Deer are killed. The Mossy Deer spawn above the wider path west of the Stu, and the boss itself spawns somewhere near the mountain cliff face up over there. If you are killing Mossy Deer in the area, you should see it as soon as it spawns. Ideally you want to fight it after Stlbk gets a strong spear, but with debuffs applied it should be at least survivable. I don't remember whether this boss had a unique item drop. Probably not.
Sharknado can be spawned in the southern peninsula of UPN Pass after defeating several sharks (probably about 10 should be enough). I don't remember where it spawns but you ideally have more than just Kuno and Beaky to fight it with. If you still want to fight it with just the original duo, I recommend bringing 200+ of cheese and pr0n. Be prepared to die several times before you manage to kill it with Beaky. He is at elemental disadvantage because Sharknado is at least 50% Water Element. It does not have any unique item drop. Farmable; appears indefinitely.
Mighty Bird appears in Hyphenistan Mountain Range and possibly spawns on the long air bridge, although which side it spawns on is unclear as I have not spawned it yet. It spawns randomly and leaving the immediate region and reentering seems to be the method on how to spawn it.
The Immortal Reactor spawns to the right of a wooden bridge over lava and only appears if a great number of sports-related enemies in the Hyphenistan Mountain Range. I do not remember whether it drops a unique item drop.
The Invading Emperor is a super tough boss that will TPK until late in Chapter 6. It is theoretically possible in Chapter 5, however it is recommended to get ultimate gears for as many units as possible before fighting it. It spawns within the silver-halled cave in Hyphenistan Mountain range, and although you can't beat it yet, you can nab the chests next to it. Its rune will only appear if you have obtained an Immortal Core, the rare drop from the Hyphenistan Mountain Range. It has a one-time drop of Kuno's ultimate armors. Probably not farmable.
Nibble is a boss that spawns within the Hyphenistan Mountain Range really close to the Hyphenistan Fortress. It spawns randomly if you've killed enemies in the Hyphenistan Mountain Range. If you can't get it to spawn, try running around the zone it spawns in killing enemies. Its rare item drop is a highly defensive accessory.
On the Raftasaurus, when it is raining, wait until the timer is at 3:30 and check the upper left corner of the Raftasaurus. If the Sea Horror hasn't appeared by then, check another Raftasaurus. It is recommended not to fight this Rune Boss with Stlbk and to wait until Loki gets Shield Attachment. If you have Muyo just spam Thunder All 3. I don't believe this Boss has a unique item drop, however I could be mistaken.
The boss Undead Monument spawns a couple floors into the basement of Ficonia Tower. A quest is required to get it to spawn, however, you must also fight the Living Monuments around the area first in order to get it to spawn. From the KamenAeons/Torkoal Stu Heal & Save floor of Ficonia Tower, you must ... (I will finish this later)
Undergrowth spawns on the penultimate floor of Ficonia Tower. By this I mean, you must go up two floors, then ignore the rude birds to go upstairs again. This floor should have several patches of green corridor as well as a vine to climb to the top floor. DO NOT climb the vine, just go to the largest green hall and fight a bunch of plants. When it spawns, Undergrowth's rune appears in the leftmost green tile, to the very west of this floor. If you enjoy hitting up and down several times, feel free to farm plant-based enemies where this rune enemy spawns. I do not recall whether this enemy drops unique items, nor whether it is farmable.
The Swamp Lord only appears when the Swamp Land is raining. You will know when it rains in the swamp region, because the rain covers the screen and its volume is super loud. Its rune spawns in the tract of land between the second house and the route to Artington. Going in the basement DOES NOT reset the weather for the swamp so you can beat the Royal Malboro along the way to the Swamp Lord! I do not recall whether the boss has a unique item drop but my gut tells me it does, and that I spent for fucking ever trying to get Loki to steal it to death in order to deal the least amount of damage to give him more chances to steal the item. Anywhoo, you should be able to beat it by Chapter 3 if you haven't already.
The Spooky Tree is a one-time boss in the upper right-hand corner of the Swamp Land. It spawns because of a quest given by an Artington NPC and I have no idea whether it drops a unique item because I didn't have Loki when I fought it. It's easy enough to beat with just your first 4 units.
The Royal Malboro is a Malboro boss that you must enter the basement to get to. After descending to the basements of hell, go south to the blue floor room and then go east until you hit the boardwalk with planks over the swampy water. You must defeat up to fifty Malboros in order to spawn it, as each regular monster has a 1 in 8 chance of spawning it. However, it spawns on the southwest part of the room near the blue room's hallway, so if you farm Malboros up near the ladder to the north, you may not see if it spawns. I believe it does have a unique item drop but no idea what because this run has mostly been me stealing the rare drop items for the first time. Aside from the Golden Rod from the Bright Fairy and the Golden Hat from the Thunder Fairy in chapter 2, I haven't stolen rare drop items frequently enough to remember who drops what.
CHAPTER 2 (Looks like a mess because it is)
EG To Fight the Shock Fairy, you need to fight Thunder enemies in the region and have a Thunder Gem drop from them. It spawns in the room immediately east of the door from Birtha's room, and if you fight enemies in that room to farm shards or Thunder Gems it should be obvious when its rune spawns. With luck, Muyo and Blastoise alone can kill it at level 7. Just stock up on healing items first, have no less than 50 cheese and animal souls before challenging it. Shock Fairy's unique item drop is the Golden Hat. Farmable; spawns indefinitely.
Shocking Vampire appears in the radioactive room filled with oil barrels south of the Birtha Door. However, the enemies that spawn in its room aren't Cheese Bats needed to spawn it, those are outside in the corridors. Honestly you're better off farming to give Muyo Thunder All 3 while trying to spawn this beast. Recommended to fight it with a full party.
Morris Worm appears in the room south-southeast of the Birtha Door in the room with a computer in it. When you talk to the computer, it says something like "An ancient evil was sealed inside." (Approximated, could be different but I am NOT leaving Pasbell to check!) Respawns infinitely; farmable. Unique item drop? I don't remember.
Mother has a prerequisite quest that you must do for an Emina Island resident to enter the region where she spawns. It is the Space Pigeon quest, and after you've unlocked the door southeast of the Birtha Door, you can enter the room where this boss spawns. She doesn't spawn in the tiny antechamber nor in the long hallway, but in the center of the big room beyond those. She appears by RNG so if she isn't there, leave the door and reenter it. I don't know if she drops a unique item but probably not. Only spawns once.
Green Dragon DW Sewer Syrup: kill all 4 types of slimes that spawn in the poisoned ponds in the western part of the Desert Wastes.
Ice Witch: Spawns randomly when there is heavy snow (Chunky snowflakes covering your screen!). Entering Wastes from Emina Gen, you go north through one sludge pool and it's up to the right 2-3 tiles off the path. You don't have to go into the second sludge pool that is the dead end; if it is not there, just head south through the sludge pond and leave the zone to try again.
DS Spectral Ice appears in Desert Shrine after you've killed a bunch of Ice Cubes. Its rune spawns near the edge of the Catwalk Peninsula north of the Stu. Corpse Party up off to the northeast of the Stu in one of the darker blue regions. You have to kill Frozen Corpses in the dark blue tiles to get it to spawn. Frozen Monstrosity: Randomly Spawns in the north area of Desert Shrine away from the Stu. If you've looked in every tunnel and it still isn't there, leave the Shrine entirely, go to town, and come back. It spawns directly south of the ladder.
CN Expensive Makeup spawns in the center when you've killed a bunch of Cursed Lipstick in the ancient drag club of Cerulean Nights. However, to get there, you will first need to kill monsters in UPN Park, collect 3 Dino-mites, bring them to the explosion NPC in Deoxys' Castle in Misconsin, and then have him give you a Dino-Mite Cluster. Then you must enter Desert Wastes from Emina Isle, go east through the first toxic puddle, and then go south into a tiny clearing with a rock. You must use the Dino-Mite Cluster on the rock to get to Cerulean Nights.
UPNPK Havok: kill ancient enemies (spawn on brick paths) first. I don't remember where it spawns Yeti: Requires a quest to spawn it, won't unlock before then. I haven't fought it yet.
VBF Unseelie: Rain, kill guardians surprise boss battle so maintain health/mana between fights Tranquil: No Weather, full stealth to tranquil lake (middle left) Fury Pixie: Heatwave. Kill Scorchies
EN Guardian Crawler - stand on rune & confirm to give it a veryberry berry (drops from most creatures in the nest & fields) Something Crawler Queen Crawler
Aura Demon Burning Aura Demon
VV Silver Lining shows up when you kill the cloud type enemies and/or pick up a silver linen from the ground. Only when you possess it does the rune spawn. You can walk onto the rume wtihout fighting it as you must stand on the rune and confirm giving up your silber linen first