The Binding of Isaac is a classic roguelike game with an extensive item selection and combos that you can pull off. It has diverging paths, variant bosses, and tons of ways to play. One of the rare features in Isaac are the transformations you can go through.
These are ways of gaining some buff after getting items from a smaller pool of thematic items, such as mom items, evil items, and mushrooms. These range from small buffs to game-changing, so it's always fun to try and achieve on a playthrough.
11 Fun Guy/Adult/Oh Crap/Stompy/Spider Baby, Bottom Of The Barrel
Here is the set of bottom-of-the-barrel transformations. While they objectively benefit your run, they leave a lot to be desired. These transformations affect the game very slightly, ranging from a singular extra heart to spawning a spider familiar. While they are not to avoid, they make up the lower tier of transformations in the game.
10 Yes, Mother? Become What You Fear
The mother transformation is pretty unique in that it gives you a weaker version of a fantastic item. When transformed, Isaac will begin dragging a knife akin to the item Mom's Knife behind him. While you can't use it as an attack, it's a decent defensive option.
It also synergizes perfectly with things that give you invincibility, so keep an eye out for those. If you get the Gnawed Leaf with this transformation, you can just go do your laundry while enemies throw themselves at you and die slowly.
9 Bob, Toxicity Embodied
Bob is a somewhat rare transformation to achieve. You have to get three items from a set of four available. Unfortunately, while still decent, the benefit is not worth seeking those items.
When transformed, you'll begin leaving behind a green creep that damages enemies while also becoming immune to poison yourself. It's an excellent passive way to damage enemies regardless of how hard it is to achieve.
8 Bookworm, Education Pays Off
Bookworm is a pretty decent transformation. 25 percent of the time, you'll shoot double tears as if you had the 20/20 item. Of course, this is a marginal buff, but with a high enough tear rate, this can become a fantastic power-up.
It's also a pretty easy transformation to achieve, especially if you stumble across a library since you only need to pick up three books. Books are very useful active items anyways, so this form is inherently good due to its requirements.
7 Conjoined, Strength Through Numbers
What's better than double tears? Well, triple tears, of course. In order to achieve this form, you need to gather three unique familiars. With conjoined, Isaac begins shooting three tears simultaneously. While the spread is a little too much to keep this transformation from greatness, it can help with crowd control and defending against flanking enemies.
The items required for this transformation are decent at best, but the payoff is surely worth it.
6 Beelzebub, The Lord Of Flies
Flying in The Binding of Isaac is always helpful. You gain immunity to traps, creeps, and ground-based attacks like spikes. You can also fly over rocks and enter curse rooms for free. Therefore, a transformation without any additional benefit that allows you to fly would be great already.
On top of granting flight, Beelzebub turns enemy flies into friendly blue ones. While the worst of the flight-granting transformations, Beelzebub is worth the effort just for being in that category.
5 Seraphim, Holy Spirit
Seraphim is another form for Isaac that grants you the ability to fly. On top of that, it gives you three soul hearts. Soul hearts are better than regular heart containers in the late game most of the time, so three extra soul hearts can be truly invaluable.
Add to that the fact that angel room items are just so powerful, and becoming Seraphim is definitely something to try and shoot for.
4 Leviathan, When Evil Takes Hold
Leviathan is the counterpart to Seraphim in that it grants you flight and two black hearts. This devilish form is slightly better than Seraphim due to granting black hearts, which damage the enemies when you lose them. Where this transformation truly shines is the item pool it uses, though.
Incredible items ranging from Abaddon to Brimstone and many more are waiting for you. Those devil room items are so strong that if you manage to transform into Leviathan during your run, you're already on the path to victory.
3 Super Bum, All The Bums Combined
Consumable items like keys, red hearts, and bombs are essential in The Binding of Isaac. However, when you get to the later floors, they drastically lose value since your ways of using them diminish. That's where Key Bum, Dark Bum, and Bum Friend come in. These familiars gather the collectibles left lying around and turn them into more valuable items. However, when you collect all three of them, they transform into Super Bum.
Super Bum acts like all three Bums combined into one but gives double the payout from each consumable. Turning useless items into valuable resources is already great, but doubling the value is just amazing. It even has a dedicated animation which is just perfect.
2 Spun, The Use Of Syringes
Spun might seem underwhelming at first, but it is one of the best transformations in the game. It gives you a flat +2 damage and +0.15 speed. A flat stat upgrade may feel not that special. However, when you consider that damage and speed are possibly two of the most important stats in the game, it begins to seem more valuable.
Especially after all the DLCs, straight damage-ups feel harder to come by, so spun is always welcome. You can gain this form by picking up three syringe items which are almost all useful by themselves.
1 Guppy, The Beloved Cat
Guppy is, without a doubt, the best transformation in the game. You have to collect or touch three Guppy items, of which there are seven items and a trinket, and you'll become Guppy. This transformation grants you flight and the ability to spawn friendly blue flies for each of your tears that hit an enemy.
That's right, for each of your tears that make contact, you gain a homing fly that deals double your damage. This transformation is so powerful that it can single-handedly turn your run from a lost one into a sure victory. With a high enough tear rate and decent damage, you'll be melting enemies' health bars in no time.