The Binding of Isaac is filled with many different helpful items that make every playthrough unique. While many can be found on a first playthrough, many more need to be unlocked by fulfilling a variety of special requirements.
The Repentance DLC for the Binding of Isaac added many of new items that shake things up for returning players. One of these new items is the Mega Mush, an item that is capable of helping players defeat the majority of bosses within mere seconds.
Mega Mush is an activated item with a base recharge time of twelve rooms. This may seem like it is too high for the item to be even worth it, but its effects are some of the very best. By using it, Isaac will be made large for 30 seconds with the effect not going away in between rooms. Isaac will additionally become invulnerable to enemy damage, have his damage increased by four times, his range increased by seven, gain the ability to destroy obstacles and doors by walking through them, and deal 1,600 damage per second by making contact with an enemy.
This item was originally created for the Antibirth mod created by fans for The Binding of Isaac before officially being added with the new DLC. It is based off of the Mega Mushroom from New Super Mario Bros with it mimicking that item's effect for this game.
With how powerful Mega Mush is, it is one of the hardest items to unlock in the game. This requirement is having all of the hard mode completion marks on every character except for the non-tainted characters. This means that Mom's Heart or It Lives, Isaac, ???, Satan, The Lamb, Mega Satan, the Boss Rush, Hush, and Ultra Greed must be completed on hard mode at least once by most of the game's characters. These characters are Isaac, Maggy, Cain, Judas, ???, Eve, Samson, Azazel, Lazarus, Eden, The Lost, Lilith, Keeper, Apollyon, The Forgotten, Bethany, Jacob, and Esau.
Unlocking Mega Mush will be difficult not only because of the difficulties, but also needing to unlock all of the characters that are required for this to work. Once players do get it however, it will make any future runs a breeze, especially if any items relating to item charges are collected. With how easy it is to quickly complete rooms, it is easy to quickly regain charges while plowing through enemies.
The Binding of Isaac is available on Mobile, PC, PlayStation 4, Switch, and Xbox One.
Source: Binding of Isaac Gamepedia