Binding of Isaac: Rebirth Wiki
The   Host
Character Isaac appearance.png
Full red heartFull red heartFull red heart
Table dividing line 1.png
Challenge Number
Starting Items
The Mulligan The Mulligan
Spiderbaby Spiderbaby
Tick Tick
Available Rooms
Item Pool Treasure Room.png: no          Item Pool Shop.png: yes
Boss Mom portrait.png

The Host is Challenge #18, starting with the items Spiderbaby Spiderbaby, The Mulligan The Mulligan, and the Tick Tick. The goal is to defeat Mom Mom. This Challenge is unlocked by default.


  • The lack of Item room isn't as well compensated by the starting items when compared to the other challenges. Isaac also doesn't start with an active item.


  • Shop Shops can sell Mom's Purse, allowing a second trinket or Smelter allowing the tick to be smelted and new trinkets to be picked up.
  • Shops can also sell Hive Mind Hive Mind, which will make blue flies and blue spiders bigger and stronger.
  • Isaac starts with one item each for the Added in Afterbirth †Spider Baby Spider Baby transformation and the Beelzebub Beelzebub transformation, meaning only two more items from each set will grant Isaac special abilities. While the lack of treasure rooms somewhat limits the possibility of completing either transformation, it is still possible:
    • Hive Mind Hive Mind counts for Added in Repentance both transformations (Removed in Repentance just the Beelzebub transformation), and is in the Shop pool.
    • The only other shop item that's in the Spider Baby set is Added in AfterbirthSpider Mod Spider Mod.
    • Added in AfterbirthSticky Bombs Sticky Bombs from Added in Afterbirth Bomb Bum.png Bomb Bum is the only other possible item for the set that appears outside the Treasure Room pool.
    • For the Beelzebub set, the only other item in the Shop pool is Added in AfterbirthJar of Flies Jar of Flies, which synergizes well with Hive Mind Hive Mind.
    • Added in RepentancePlum Flute Plum Flute, another Beelzebub set item, can be easily acquired by not attacking Added in Repentance Baby Plum Baby Plum for about 30 seconds.
    • Skatole Skatole, another Beelzebub set item, can be won from Shell Game.png Shell Games, which are likely to spawn in Arcade Arcades.
    • Key Master.png Key Masters have more than a dozen fly items that contribute to the Beelzebub set that they could pay out with.
    • Isaac still produces flies when firing at lowered Host Hosts, so it is possible to farm flies off of them



  • A host is an organism that is infected by a parasite, which explains why Isaac has items and trinkets relating to parasites.
  • This challenge is similar to the 'Lord of the Flies' challenge in the original game.