The maker of Candy Box is named aniwey (with a lower case a.).
The Developer is also a boss in the castle. He throws magic at you and if you attempt to erase it using a spell, you get killed. A message comes up that says, "Eh, he is the developer after all". He gives the Y stone upon defeated.
The first text, "HELLO", is made of magic balls that deal 20 damage per hit.
The second text, "I'M GLAD YOU MADE IT THIS FAR", deals 32 damage per magic ball.
The third text, "<3", deals 9,999,999,999,999 damage per magic ball.
The Developer has 1,000,000,000 HP, but takes 60,000-70,000 (random) times base damage.
If the player uses black magic, Black Hole, or Erase Magic, a black hole will be formed at the player's location, dealing 5000 damage per hit. Teleport can dodge the Black Hole, but spell cooldown prevents Teleport from being used right after another spell, so it can only be used after your own Black Hole. The Developer's Black Hole will damage himself.
The Developer drops 6,000,000 candies upon defeat, and logs the message, "You managed to beat me. Congratulations :)".
When he dies, he drops the The Y stone.
Overview: Cause the Developer to cast Black Hole while standing next to him, and then survive the Black Hole long enough for the Developer to die from it. Requires more than 2000 HP and Enchanted Knight's Armour, or more than 1000 HP if also using Turtle Potion. To trigger his Black Hole, just cast Erase Magic, Obsidian Wall, Black Demons, or Black Hole.
The Developer takes damage from his Black Hole at 30% to 35% max HP per tick. That means it takes three to four hits for him to die from it. The less HP he has, the more likely he'll die from 3 ticks instead of 4. At 90% HP, he'll always die in 3 ticks.
If both the Player and the Developer die at the same time, the Player wins. Therefore, the Player must survive three ticks, possibly dying on the third.
Surviving three ticks
With Enchanted Knight Body Armour, the Player takes 1000 damage per tick instead of 5000, so at least 2001 (current) HP is needed. With the Armour and Turtle Potion, the Player takes 500 HP per tick, needing 1001 HP. With the Armour, Turtle Potion, and 1501 HP, the Player can live for 4 ticks and guarantee the Developer's death.
Two Health upgrades with heart pendant, heart plug, and at least 793,653 candies eaten will result in more than 2000 max HP. Even with max HP from eating candy, more Health upgrades won't allow surviving more Black Hole hits until the 5th upgrade, but they allow the Player to hit the Developer for a longer period of time.
If you Jump at the same time that you cast a forbidden magic, you will only take two ticks of damage, and the Dev will die even if he survives the first three ticks. This method still requires surviving two ticks of damage (e.g. Enchanted armor and 2001 HP).
Instead of taking the damage, the Player can also Teleport away from the Black Hole. The only way to do this is to cast your own Black Hole and immediately Teleport away, hoping that you don't teleport into a Black Hole.
Turtle and Black Hole
Have 2 Turtle Potions ready, and use them when the Developer's first and second text messages are about to reach you. The third one will instantly kill you, so just before that one reaches you, nuke him with the black hole spell and defeat him. Keep in mind, though, that if you use the black hole too soon, he will kill you with his own. Likewise, if you use any magic, at any time, he will instantly wreck you.
An easy way to kill him is to equip rocket boots, hold J (if you have the pogo stick enhanced with the feather from the desert bird) or repeatedly press the jump key to fly as high as is permitted and land on his head. Use a turtle spell and cast a black demon or black hole spell, thus causing him to cast his own black hole spell on himself, instantly killing him.
The Developer gives 6 million candies, and can be farmed effectively with the Merchant's Hat increasing the reward to 42 million. Health Potions are easy to make, if you equip the Boots of Introspection and go to the spike room in the castle it's easy to spam them and heal very quickly between fights as long as you have all the passive healing items in the game.
Note that this strategy is mentioned in the Y Stone.
These are builds that players have contributed.
First, enchant as few items as possible throughout the game. This is so you can make as many pains au chocolat as possible. put AT LEAST four into getting "more power" as this gives you an 80% attack boost. Put any remaining pains au chocolat into health. Ignore magic for now. So long as you have the claw that gives you a *2 boost to attack power, and an unenchanted knights armor, and the scythe equipped, brew up a couple turtle potions and take him on. (For hardmode you'll want the Giant Spoon of Doom instead of the scythe.) Take the turtle potion as soon as the first wave is about to hit you. Waste any time jumping or you might take too long. Deadly third wave is deadly.
Do not equip the enchanted armor! This will leave you with too little attack power to kill the developer before the third wave hits you.
First, get two pains au chocolat and use them for health and attack. Be sure to be at max health. Equip the octopus's crown with jaspers, pink enchanted gloves, scythe, rocket boots, and knights body armor. Be sure to have the unicorn horn and xinopherydon claw, as these are essential. Begin attacking the developer and squeeze. Then use a cloning potion and jump to the highest place possible. Use a turtle potion, and then a berserker potion and before the second wave hits the developer should die.
Equip the Giant Spoon of Doom, the Octopus King crown with jaspers, the unenchanted knight's body armor and the pink leather gloves. Be sure to have the unicorn horn and the xinopherydon claw. If you have enough health and attack gifts, the developer should die before the second wave.
It's possible to beat this boss using only the Giant Spoon of Doom, the Xinopherydon Claw, one upgrade (Power or Magic), the Lightweight Body Armor, and a couple potions. You need to have a minimum of 1180 HP or as little as 955 if you are using the Pink Leather Gloves.
As soon as you get to the boss, use one Berserk Potion. If your upgrade was not into Magic, you'll want to spam the Turtle Potion to trigger it as soon as possible. Otherwise, wait until the "HELLO" starts moving towards you to use it. When the timer resets, use another Berserk potion. The boss should run out of HP right before the second wave hits you.
It's possible to use this same method with the Scythe if you have one upgrade in each Power and Magic.