Tainted Apollyon

What you start with

The mechanics that actually govern this character.

• 2 red heart containers, tears -0.5, one red locust familiar, and Abyss in the pocket slot on a 4-room charge.
• Abyss destroys every item pedestal in the room and turns each destroyed item into a permanent locust that charges in the direction you are firing and damages what it hits.
• On 1.7.9 locusts deal your FULL damage per tick regardless of the item eaten. The quality-based scaling (0.5x for quality 0 up to 2x for quality 4) is a Repentance+ change and does not apply to your version - so do not plan around eating high-quality items for stronger locusts.
• Locust cap is 64 and it is shared with blue flies and blue spiders; exceeding it replaces the oldest. Locusts are near-permanent: only Genesis wipes them, and D4, Missing No., Tainted Eden rerolls and similar cannot touch them.

How to play them

• The gimmick in plain language: you convert items into permanent damage. Every pedestal is a decision - is this item worth more than a locust is?
• Because 1.7.9 locusts scale with your damage STAT rather than the eaten item's quality, the maths is simple: eat the junk, keep the damage. A quality 0 item makes exactly as good a locust as a quality 4 item does.
• Your tears are terrible at -0.5, so The Sad Onion, Torn Photo and similar are usually better kept than absorbed. You need a baseline gun for the rooms where locusts are badly positioned.
• Choice rooms are a trap for locust farming: Boss Rush, alt-path Treasure Rooms, More Options or There's Options rooms and some Angel Room layouts give only ONE locust for the entire set. Libraries and other take-everything rooms give one per item and are enormously valuable.
• If you are already at 64 locusts and face multiple non-choice pedestals, Abyss only consumes half of them.
• Using Abyss in a Boss Rush or a Challenge Room counts as taking the item and starts the waves, so it is not a free absorb.
• A good run feels like a swarm building floor by floor. A bad run is one where you ate your damage items and now have 20 locusts each doing 3.5 damage a tick.

Items to hunt for

Strong on this character specifically, not just strong.

• Birthright: locusts stay deployed and track the enemy's position for as long as you hold fire. It converts the character from an aiming puzzle into a shredder and is by far the largest upgrade available. Combined with the Guppy transformation, every damage tick counts for Guppy, producing a constant stream of blue flies.
• Hive Mind or BFFS!: both greatly boost locust damage, which makes Shops a routing priority. They do NOT stack, so buy one, not both.
• Extension Cord: every locust generates an electricity beam between them, which massively extends your effective reach and coverage.
• Ipecac: keep it, do not eat it. Its damage bonus applies to every locust you own, which scales far past the single poison locust you would get from absorbing it.
• Boss pool damage items generally, for the same reason: your entire kit multiplies off the damage stat on 1.7.9.
• Worthwhile special locusts on Repentance if you must feed something: Cricket's Head gives a larger triple-damage locust, Blood of the Martyr gives a double-damage locust, Holy Light gives one that calls down 3x-damage beams, Spoon Bender gives a homing locust, Mutant Spider gives 4 locusts and The Inner Eye gives 3.

Traps to refuse

Picks that are neutral or good elsewhere and bad here.

• Genesis: removes every locust except your starting one and does not replace them with items. On this character it is close to run-ending.
• Soy Milk: a large tears upgrade that drastically cuts locust damage. On this character it is usually better absorbed for a locust than taken.
• Sacrificial Altar and exceeding the familiar cap will both eat locusts you already earned.
• Careless Abyss timing while swapping actives - the old active you are holding above your head gets consumed too, which is easy to do by accident when you meant to keep it.
• Do NOT copy the Repentance+ advice about eating Broken Shovel for a quality-4 locust. Quality scaling does not exist on 1.7.9, so it is just an ordinary locust and you gave up your active slot to get it.

Cheese and techniques

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

• Buy first, eat after. Like Void, Abyss can consume an item you are holding above your head, so you can purchase a shop item and immediately turn it into a locust. Best value on one-use items you would not want anyway, such as Mom's Coin Purse or Booster Pack.
• Blind pedestals (alt-path Treasure Rooms, Curse of the Blind): pick the item up and hold Abyss ready, then absorb it at the last second if what you see is bad. This is a free look at every blind item in the run.
• Soul of Lilith familiars and any unwanted bought item can be destroyed the same way.
• Glowing Hourglass locust duplication is live on 1.7.9: teleport back to the previous room with it and use it again to duplicate locusts. Glowing Hourglass has 3 uses per floor on Repentance with unlimited recharge.
• Locusts break rocks, which opens regular doors and Secret Room entrances without spending bombs. They also survive the Knife Piece 2 sequence and help burn away the Fire Places blocking the path, even though Mother's Shadow itself cannot be hurt.

Getting the marks

• 7 secrets. Isaac, ???, Satan and The Lamb collectively unlock Cricket Leg. Mega Satan gives Rotten Beggar, Boss Rush OR Hush gives Soul of Apollyon, Greedier gives the XVI - The Tower? card, Delirium gives Abyss, Mother gives Apollyon's Best Friend, The Beast gives Echo Chamber.
• Boss Rush is a bad place to spend Abyss - the multi-item choice sets give one locust each and absorbing starts the waves. Take the item instead and beat it with your existing swarm.
• Mom's Heart and normal Greed give no secret for tainted characters; both marks still need filling for the note and for Death Certificate.