Suicide King is Challenge #7. Lazarus is the default character for this challenge, and he starts with Ipecac, Mr. Mega and My Reflection, as well as a random pill. The goal is to defeat Isaac. This Challenge is unlocked alongside It Lives!.
Though Ipecac and Mr. Mega would be a powerful build in a normal run, My Reflection causes tears to loop back around towards Lazarus, forcing him to have to avoid not only enemy tears but his own as well. This also makes aiming tears significantly harder.
The 1 pip and 6 pip dice rooms will not reroll the starting items for this challenge but will reroll any others.
Lazarus has one extra life by default, granting him some survivability.
Because of My Reflection, the range is diminished. With a little practice, however, it can be easy to tell how far away the shot will travel. Lining up enemies with that distance will make it easier to score direct hits that won't come back. One way to track this is by the shadow of the Ipecac tear.
Ipecac's explosive tears can be used to break rocks, mushrooms, and skulls, and open secret rooms.
Crawl Spaces are very valuable because of the lack of Treasure Rooms, making the destruction of all encountered rocks a viable strategy. Most items that can be acquired this way are useful, but Pyromaniac, Dr. Fetus and Host Hat are especially noteworthy for their ability to prevent all self-damage inflicted on Lazarus.
It is worth noting that Dr. Fetus, unlike Pyromaniac and Host Hat, will not prevent any damage inflicted by bombs, but it will massively increase Lazarus's damage in exchange.
If properly aiming the Ipecac shots while simultaneously dodging them proves too challenging, some familiars or orbitals can serve as a consistent means of dealing damage without firing tears.
Grouping enemies together is an effective way of clearing rooms while minimizing the amount of tears needing to be fired per room.
Because Ipecac also increases the damage of Blue Flies and Blue Spiders, obtaining an item that spawns them can be extremely useful.
It is possible to hit enemies without having to worry about My Reflection by moving in tandem with the Ipecac tear, making the shot faster. This method only works with a higher Speed stat.
A higher Shot Speed stat allows the tears to fly further away from Lazarus before returning, allowing enemies to be shot from further away while reducing the risk of being caught in the blast radius.
The Magic Fingers item is a common shop item that is affected by Ipecac's damage increase. This makes it extremely viable as an alternative damage source to Ipecac tears, especially in runs with a large coin count.
If Envy is encountered, and it drops Shoop Da Whoop!, it is highly advised to pick it up. Due to the item's relatively quick recharge time, and the fact that its damage is greatly increased by Ipecac, it can be used as an ace in the hole to clear challenging rooms and easily defeat bosses.
Mom's Knife or Brimstone can be purchased from a Devil Room if found with a Red Chest or using Goat Head, overriding Ipecac and making the challenge much easier. Death's Touch allows the tears to do damage in-flight, making it significantly easier to hit enemies.
Hook Worm and Whip Worm are both useful trinkets and should be collected if possible.
Hook Worm allows tears to hit enemies more easily, while also making them easier to avoid by Lazarus.
Whip Worm forces tears to fly very fast and low, usually preventing enemies from dodging them. It also makes tears that hit the edge of the screen explode rather than coming back to Lazarus.
Gnawed Leaf is another useful item from crawl spaces causing Lazarus to turn into a statue just before the Ipecac tears hit him. This is only really useful for destroying objects.
Succubus is an incredibly useful familiar, as its damage scales with Lazarus's. Succubus allows the challenge to be cleared without using tears as it only takes a few seconds for it to clear out a regular-sized room autonomously.
Familiars that mimic Lazarus's tears, such as Fate's Reward, are not recommended for this challenge. While they do increase Lazarus's overall damage output, they are very difficult to avoid, as they are usually fired directly towards Lazarus.
The Devil Room at the end of the It Lives boss fight will contain regular Deals with the Devil instead of a trap door, as the challenge requires Lazarus to go to the Cathedral.
If the player somehow manages to end up going to Sheol instead of The Cathedral (i.e. through a trapdoor in The Womb II), defeating Satan will successfully finish the challenge and erroneously unlock the achievement.