Apollyon

What you start with

The mechanics that actually govern this character.

• 2 red heart containers and Void, a 6-room-charge active in Repentance (Repentance+ dropped it to 4; on 1.7.9 it is 6).
• Void destroys every pedestal item in the room. Each passive eaten gives 2 random stat boosts from: +1 damage, +0.5 fire rate, +0.2 speed, +0.2 shot speed, +1 luck, +2.5 range. Each active eaten is permanently added to Void, and every future Void use fires all stored actives in absorption order.
• Stat gains are seeded to the count of items absorbed, not to which items, and they survive dropping Void. They do NOT survive a D4 or D100 build reroll.
• Repentance change to know: absorbing from a choice pedestal room (More Options, There's Options, Blue Womb treasure rooms) only consumes ONE item, the other vanishes. The Afterbirth+ double-absorb is gone. A newly absorbed active also no longer fires immediately; it fires on the NEXT Void use.

How to play them

• Apollyon converts bad luck into stats, so his floor plan is different: clear the whole floor, leave every junk pedestal standing, then Void them all in one room, or ferry them together with Moving Box.
• Take quest items for free stats. Knife Piece 1 in Downpour II can be absorbed if you are not going for Mother, and Key Piece 1 and 2 respawn after each Uriel or Gabriel kill no matter how often you Void them, as long as you never actually pick one up.
• A Library is a jackpot: every book is an active, so Void turns the room into a multi-effect nuke button. Touch at least three books before absorbing to bank the free Bookworm transformation.
• Do not absorb The Bible (Void auto-fires everything it holds, and The Bible instantly kills you during the Satan fight), and do not absorb Book of Virtues (Void treats it as a passive, so you trade the wisp engine for two stat rolls).
• How to Jump inside Void causes an uncontrolled lunge every activation and can wedge you behind rocks; skip it.
• Do not Void inside Boss Rush or a Challenge Room unless you want the waves to start - absorbing counts as taking the item.

Items to hunt for

Strong on this character specifically, not just strong.

• The Battery, Sharp Plug, Charged Baby or 4.5 Volt: any of these lets you fire Void twice back to back, which is how you nuke a boss and then still eat the boss drop without leaving the room.
• Birthright: each Void use has a 10% chance to spit one previously absorbed passive back onto a pedestal while you keep the stats it already gave. Duplicates each roll separately, so absorbing the same item repeatedly raises the odds.
• Goat Head or Eucharist: guarantees the deal room is already open when the boss dies, so one Void charge covers both the fight and the deal pedestal.
• Anything that makes more pedestals exist: Damocles, Diplopia, Crooked Penny, Death Certificate. More pedestals is literally more stats.
• Alabaster Box: with Void it can be charged by normal room clears rather than only by soul hearts.
• Glass Cannon: absorbed into Void it fires every activation and can never break or hurt you.
• Eraser: once inside Void it can be used more than once per floor, letting you delete several enemy types from the run.

Traps to refuse

Picks that are neutral or good elsewhere and bad here.

• Satanic Bible in the Void: it replaces your boss drop with a Devil Deal, and unpaid Devil items cannot be absorbed until you pay for them.
• D4 and D100: rerolling your build wipes every stat gain Void has given you. This is the one thing that undoes his whole run.
• More Options and There's Options are far weaker for him in Repentance than in Afterbirth+ - a choice pedestal now yields one absorption, not two. They are still fine for copying active item effects.
• Absorbing Book of Virtues, Moving Box, or any active you actually wanted to use. Moving Box specifically converts into stats instead of being added to the actives list.

Cheese and techniques

Verified against 1.7.9 on console — anything patched, PC-only or Repentance+ only is called out rather than listed.

• Void during the item-get animation. In Repentance you can use Void while the item is still held over your head, so you can buy a Devil, Black Market or Shop item, pay for it, and eat it for stats. It also works on Blind Curse pedestals and Downpour treasure rooms - pause to read what you grabbed, then decide.
• The same trick absorbs the familiars a Soul of Lilith card gives you, and absorbs a second active if you have Schoolbag with an empty second slot.
• Key Piece farming: fight the angel, absorb the Key Piece plus the unwanted angel item together, and the Key Piece spawns again next time you kill an angel. Free stats every Angel Room while still reaching Mega Satan later.
• Devil Deal shopping without commitment: keep 15-30 cents or a spare heart specifically to buy an item you only want as raw stats, since deals must be paid before they can be absorbed.
• Not on 1.7.9 in its old form: Afterbirth+ let Void absorb an uncharged active and immediately fire it. In Repentance the newly absorbed active only goes off on the following Void use, so budget an extra charge.

Getting the marks

• Non-tainted, 14 secrets, all Hard marks unlocks Apollyon Baby.
• His marks are almost the entire Locust trinket set: Mom's Heart gives Smelter, Boss Rush gives Locust of Conquest, Isaac gives Locust of Wrath, ??? gives Locust of Famine, Satan gives Locust of Pestilence, The Lamb gives Locust of Death.
• The rest: Hush gives Hushy, Mega Satan gives Mort Baby, Ultra Greed gives Brown Nugget, Ultra Greedier gives Black Rune, Delirium gives the Void item for other characters, Mother gives Lil Portal, The Beast gives Worm Friend.
• Do the Mom's Heart mark first for Smelter. Once you have it, every Locust you unlock afterwards can be eaten permanently, which makes his later marks noticeably easier.