Challenges

**Challenges** are unique runs in the game. Isaac typically starts each challenge with one or more specific items which makes normal play more difficult. With few exceptions, Treasure Rooms are not available during challenges. Each challenge unlocks new content for the game, such as runes when completed. Players, with the advent of modding, have created their own Custom Challenges too.

## General Strategy

Most challenges are designed to increase the difficulty of the game in a unique fashion. This doesn't mean all challenges are especially difficult. Challenges like Computer Savvy can be quite easy to beat, other challenges compensate for this by being especially punishing; Solar System being a good example of this. Each challenge has certain strategies that can be employed to make the run easier. However, there are a few strategies that can apply to all challenges.

* Challenges can be played in co-op, allowing a second player to contribute to the run without being hindered in the same way Isaac is. This is especially useful in any challenge where Isaac is Blindfolded, as the second player will be allowed to fire tears normally.
	+ If other players join the game in the first room for true co-op, they will not get to select a character and will be forced to play as the character the challenge has you play as, ex. for Blue Bomber, all players will be forced to play as  ??? no matter what. (This excludes untrue co-op because of co-op babies.)
* Due to the lack of Treasure Rooms, Devil Rooms become much more valuable. Some challenges can be made much easier by making just one deal, but it is worth noting that other challenges reduce Isaac's health to the extent that Devil Deals become too risky.
	+ Some rooms (including Crawl Spaces) may have Treasure Room items by default. Since these items are random, results can vary from run to run.
		- It makes useful, since it can open Crawl Spaces each floor.
	+ Because locked Treasure Rooms won't spawn, keys can be used far more liberally. Also, trinkets and items that generate more coins, along with upgraded Shops, can help Isaac acquire a greater range of powerful items.
* instantly kills Mom and Mom's Heart / It Lives. All challenges require defeating Mom, and most require defeating Mom's Heart or It Lives, making this an extremely powerful item, especially in challenges where Mom or Mom's Heart / It Lives is the final boss.
	+ will spawn  if used in Womb/Utero/Scarred Womb II, making it a reliable way to acquire The Bible.
	+ can also do 's job.
* Curse Rooms can spawn items, making them valuable.
* In some challenges, Dice Rooms and the  are very useful, allowing that challenge's starting items to be rerolled, thus removing most of the difficulty. NOTE: This changes depending on the challenge. Most challenge pages contain details on the results of rerolling.
	+ can also remove starter items.
* Blindfolded challenges are arguably the most difficult challenges due to Isaac's inability to fire tears. There are several methods to work around this.
	+ Familiars can provide an alternative method of dealing damage. Powerful familiars like ,  and  are therefore highly useful items.
	+ , , and  are also useful for blindfolded challenges, since they recharge based on a timer, rather than an amount of cleared rooms.
	+ Golden Bomb also provides a powerful damage output method for a floor.
	+ can allow Isaac to change into  Lilith, whose  overrides the blindfolded effect by default.
	+ Some active items like  can be really helpful, providing an alternative method of dealing damage.
	+ ,  and  can be charged and fired even while Blindfolded, giving you very powerful attacks when you're not supposed to be able to shoot.
* is a powerful item in challenges, as it can allow powerful items to be found more commonly, such as in the Shop or after defeating bosses.
* Defeating a boss beyond the specified end of the challenge (e.g. defeating Mom's Heart when the goal is to defeat Mom) will still spawn the trophy.
	+ In some longer challenges (e.g. XXXXXXXXL), using a Sacrifice Room until it teleports Isaac to the Dark Room is a viable strategy. Once in the Dark Room, the trophy can be spawned by defeating The Lamb.
		- In a similar vein, all runs can be completed by killing Delirium, meaning that the player can beat a challenge through an alternative method such as defeating Hush then traveling to The Void; however, this is generally extremely difficult given the restrictions challenges place on the player.

## Notes

* Apart from the achievement related to beating the challenge, all achievements are locked. Also, no Donation Machines will appear in any challenge.
* The challenge reward will not be unlocked unless the trophy is picked up. If a Devil Room, Angel Room or Black Market appears allowing Isaac to go to Sheol or the Cathedral, the unlock will be forfeited.
	+ If Isaac goes to the Cathedral using , the unlock will also be forfeited
* Isaac will not start any challenge with .
* Items with tag `nochallenge` are excluded during challenges.
	+ , ,  and  are excluded, preventing Isaac from changing to other characters.
		- is still available.
	+ is also excluded.
	+ Excluded items are considered as if they have not been unlocked, thus it is not possible to get these items by ,  or .
	+ It is, however, possible for Aprils Fool (challenge #32)‘s effect on active items to cause  to activate.