The Headless Horseman is spawned when a Horseman's Candle is used under valid conditions. Horseman's Candles can be purchased from the Fear Mongerer for 32Purple Candy.
The Candle must be used under valid conditions in order to spawn the boss:
Upon death, the Headless Horseman turns the ground under its death point to obsidian in a 2 block radius.
A message is displayed in chat announcing to the server that it has been defeated, who dealt the final blow, the top 3 damagers, and the player's damage, position, and gained Runecrafting XP and Bits, similar to the message displayed when a boss dies. There is also a beacon that displays the location of the boss's defeat: its drops appear around the beacon in the obsidian radius.
The player who summons the Headless Horseman will receive 4Spooky Fragments. The player who places first in damage will receive 1Spooky Fragment. The player who places second in damage will receive 0–1Spooky Fragment.
The Headless Horseman cannot be damaged by Arrows and the Bonemerang. Attempting to damage it with a projectile will reel the player towards the boss and blind them for 3 seconds.
When spawned during the Spooky Festival, the Headless Horseman does not respect the player's invincibility frames, meaning it can kill them very quickly.
This bug does not happen during the hour before and hour after the Spooky Festival while the Fear Mongerer is in the Village.
The Headless Horseman, unlike most other bosses, can spawn as Runic. Its runic version has only 10,000,000 instead of the expected 12,000,000.
The Headless Horsemantechnically has a head; however, its head is a jack-o'-lantern, similar to its original appearance in The Legend of Sleepy Hollow, where the Headless Horseman originated.
It was possible to use the Headless Horseman to remove Bedrock on the player's Private Island on ☀ Stranded, but this was later patched.
The Headless Horseman gives an average profit of ??? coins for the summoner, or ??? coins for a group of three.
It therefore costs ??? coins to complete the Bestiary alone, or ??? coins as a group.
["Echolocator","Horseman's Candle","Bat Firework","Bat Person Armor","Spooky Armor","Intimidation Artifact","Intimidation Ring","Bat Artifact","Bat Ring","Candy Relic","Candy Artifact","Candy Ring","Candy Talisman","Trick or Treat Bag"]
["Snowball","Ice","Red Gift","Green Gift","White Gift","Gift","Frosty the Howitzer","Frosty the Snow Blaster","Frosty the Snow Cannon","Defend Jerry's Workshop"]
["Glacial Artifact","Glacial Ring","Glacial Talisman","Glacial Fragment","Glacial Cave","Snow Minion#XII","Ice Minion#XII","Snow Necklace","Snow Gloves","Snow Belt","Snow Cloak","Gold Gift Talisman","Purple Gift Talisman","Blue Gift Talisman","Green Gift Talisman","White Gift Talisman","Reindeer Pet","Einary","Jingle Bells","Fried Frozen Chicken","Frozen Chicken","Gift Compass","Chicken Race"]
["Winter Island (Item)","Fragmented Cryopowder","North Stars","Golden Gift","Gift the Fish","Snowman Pet","Grinch Minion Skin","Present Stack","Snow Suit Armor","Gingerbread Man Minion Skin","Santa Minion Skin","Winter Disc","Battle Disc","Tall Holiday Tree","Bottle of Jyrre","Ice Rune","Snow Minion","Skill XP Boost Potion"]
["Glacial Scythe","Winter Water Orb","Rusty Anchor","Salt Cube","Flake the Fish","Walnut","Nutcracker Armor","True Ice","Hunk of Blue Ice","Hunk of Ice","Ice Bait","Yeti Rod","Auger Rod","Winter Rod","Ice Rod","Festive Sinker","Icy Sinker","Reindrake","Nutcracker (mob)","Grinch","Frozen Steve","Frosty (mob)","Yeti"]
["Snow Minion#XII","Ice Minion#XII","Snow Necklace","Snow Gloves","Snow Belt","Snow Cloak","Gold Gift Talisman","Purple Gift Talisman","Blue Gift Talisman","Green Gift Talisman","White Gift Talisman","Reindeer Pet"]