The Binding of Isaac: Rebirth

In order to unlock this item and the achievement that bears its name, you first need to unlock Eden (a playable character) and Sheol (an area where Satan is the boss). That means you need to have unlocked the following achievement:



You can read the solution there, but in essence you just need to beat Mom's Heart in the Womb for the first time. That's easier said than done, but you will reach the point in this game where you find that boss is quite easy if you keep at it. This solution will be more focused on making it that far and further still with Eden, along with some advice for the Satan boss.

Playing Eden

Playing Eden requires Eden Tokens, which you earn by beating Mom's Heart (and a few other bosses that may be a spoiler to mention). This means you need to have previous fairly successful runs to even have a chance to play as Eden. For this reason, I recommend having at least a dozen or so tokens before going for something specific like this achievement. Starting a run consumes a token, creating a new Eden with random base stats and two random starting items. One of those items will be passive and the other will be active. Eden might also start with some coins, keys, bombs, and/or single-use items. All of this means your success will partly depend on RNG. But that's always true in this game, so don't worry and try to make every run a success.

Eden's randomness makes it difficult to give specific advice regarding the character, but general advice applies just as well to Eden as it does to characters like Isaac. There are a LOT of ways to play Binding of Isaac, but I can tell you what I do to try to maximize my chances of making every run a success. To begin with, I try my best to take my time and explore every room I can without taking red heart damage. If I've already taken red heart damage on the floor, there is no reason to do anything other than fully explore it unless I'm worried I will die. This helps you find more items, more coins to buy items in the shop, and more red hearts to heal yourself before/after boss fights.

In Binding of Isaac, success snowballs. In other words: the more you have, the more you earn. This makes the first few floors extremely important to fully explore. If you have spare bombs and have not found the hidden room, search for it by bombing center walls near empty spaces on the map. Look for empty spaces that are adjacent to at least 3 other rooms with unblocked walls connecting to that empty space. If a bottomless pit, rock, spikes, or some other obstruction blocks the middle wall space that would be the entrance to the hidden room if it was there, there is definitely no hidden room there.

Reaching Satan

If you have not yet unlocked the Negative achievement/item, then you will need to hope that Sheol spawns after beating Mom's Heart. The chance of spawning can be seen if you turn on the stats UI in the settings. You can increase this chance by avoiding red heart damage and entering devil rooms when they appear. Avoid entering Angel Rooms if you want to go to Sheol and you have not unlocked the Negative. If you HAVE unlocked the Negative, picking it up after beating Mom guarantees that the trapdoor to Sheol will spawn. When the trapdoor spawns, you must enter it to reach Sheol. Entering the light and going up to the Cathedral will lead you to a different boss. Also, you can reach Sheol whether or not the trapdoor spawns by using an item that lets you go down a floor.

If you start your run planning to go to Sheol, be aware of the layout of it. Sheol has no treasure room or shop. It is likely that you will only take damage as you search for Satan's boss room unless you're having a very good run. So, bringing an item such as the Emperor card, which allows you to warp straight to the boss, may be a good idea. If you plan to do that, try to enter Sheol with full health and a fully charged use item.

Sheol's enemies are tough, and many (or most) of the rooms will have a boss or several bosses in them instead of normal enemies. However, unlike previous areas, Sheol has only one floor. So, heading straight to the boss room is usually your best bet. If you can't teleport there, an item that gives you the full map or otherwise shows you the boss location can be very helpful.

Defeating Satan

I'm not going to sugarcoat it. Satan is hard. If you're not careful, he can swiftly end what otherwise seems like a great run. However, with practice you can beat him nearly every encounter. One of the reasons he is so tough is that his fight is LONG, featuring 3 distinct phases that each have their own full health bar. I'll go over the 3 phases and the strategy for them below. Remember that throughout this entire fight, you will take a full heart of damage if you get hit (unless you have certain items). Also, if you have the Bible, DO NOT USE IT. You will die instantly.

Phase 1: The Fallen
When you enter the room, there will be a slight delay. You can take advantage of this delay to activate items that last the entire fight. As with any boss, bringing in such items can make the fight, much, much easier. This is especially true of things that increase your damage and/or give you psychic shot. In front of the statue, The Fallen will appear, along with two kamikaze leeches on the left and right of it. Kill the leeches ASAP, keeping in mind that they explode. Those explosions can hurt you, but they can also hurt the Fallen. The Fallen itself has 2 phases. During phase 1, it moves about randomly in cardinal directions and uses one of its 2 attacks. Usually, it will fire 3 projectiles in a spread immediately followed by a spread of 4 more directly at you. Squeeze between these shots as you can, bearing in mind that the second shot will usually go around you if you're standing still. Sometimes, it will get angry and begin to chase you. This is a good opportunity to do a lot of damage, but note that the moment it stops chasing you and sits down, it will fire brimstone lasers in all 4 cardinal directions, so you need to be diagonal to it. At 50% health, the Fallen splits into two smaller but otherwise identical versions of itself. Both of these Fallen have the same two attacks listed above. Obviously, this is a much tougher phase so it would be a good idea to focus on killing one of them as quickly as possible so you can get back down to only fighting one Fallen at a time.

Phase 2: The Statue
As soon as the Fallen dies, the devil room statue transforms into Satan and the real fight begins. I recommend you move to the left or right side of the room at this point. Satan will stay at the top of the room and move horizontally, performing 3 different attacks. One attack is a half-ring of 8 projectiles he shoots from each hand towards the left and right sides of the room. If you're standing to the side, squeeze between them and keep firing. The other projectile attack is when he spits out 2 consecutive spreads of 5 and 4 projectiles towards you. He always chains this attack at least twice, but can do it more. This is similar to the spread attacks from the Fallen, but a little harder to dodge. The spread of 4 can still usually be dodged just by standing still and waiting for them to go around you, but you'll need to move quickly afterwards. Now, his third possible attack is the reason I advised you to stand to the side during this fight. If you're standing below him, he will often shoot two brimstone lasers from his hand that curve toward each other, leaving a gap in the middle, and/or he will charge up and fire a brimstone beam from his mouth straight downwards. These brimstone attacks can be fast and annoying, so I recommend sticking to the sides and weaving through the blood flying at you, shooting towards the middle as you go. It will be hard not to take damage during this phase, but usually this is the hardest phase of the fight.

Phase 3: The Hooves
After depleting the phase 2 health bar, the third and final health bar appears. Satan flies off screen and now only has one attack. He stomps the ground with both of his feet at your previous positions, similar to Mom's stomp attack but with less delay. The stomps come down one after another and after two stomps they persist a moment before both are retracted. This means you need to keep moving during this phase, being careful not run into the legs but also careful not to stand still if one of the legs is up in the air. Now, this would be pretty easy if this was all that happened, but... up to two kamikaze leeches continuously spawn while this happens. The good news is, these leeches can be killed by the stomps and they deal considerable damage to Satan. The bad news is, they rush towards you, so they're more likely to damage you than Satan in my experience. My advice is to kill the leeches as they appear, because they are usually what makes this phase of the fight difficult. Without the leeches, you're just moving about and shooting at legs that are stomping positions you left a long time ago.

When the third and final health bar is depleted, Satan is destroyed. Any remaining leeches will die alongside him. Congratulations! You've unlocked yet another item and yet another achievement! Keep it at it, because Binding of Isaac has much more to offer, including several bosses that, believe it or not, are much tougher than Satan. Eventually, you'll feel like beating Satan is a pretty quaint accomplishment.