- 黏黏的五美分 - 完成Boss Rush关
- 超级贪婪宝宝 - 击败困难模式的妈心或它还活着！
- 店主的 商店钥匙 - 击败撒旦
- 店主的 木质硬币 - 击败以撒(boss)
- 福报 - 击败羔羊
- 深口袋 - 击败???(Boss)
- 贪婪的肋骨 - 击败究极贪婪
- 店主现在拥有了……一分钱！ - 击败Hush
- 吊绳宝宝 - 击败超级撒旦
- 特惠宝宝 - 在困难模式下获得所有通关标记
- It's usually a good idea to use the Wooden Nickel right after entering a room, because that way, a coin dropped will also work as emergency healing.
- The Battery, 9 Volt, Charged Baby and Car Battery help to further increase the amount of coins produced. Having Habit will recharge the Wooden Nickel whenever you're hit, allowing Keeper to potentially sustain itself endlessly, as long as the Nickel pays out.
The following shop items are particularly useful for Keeper:
- 虫群之心: Enhances the many Blue Flies Keeper will naturally produce.
- 永远的好朋友！: Any Orbital Familiars are important to protect Keeper's low health, so increasing their size always is good.
- Piggy Bank: Drops 0-1 coins with Keeper instead of 1-2, but still provides increased survivability.
- 妈妈的盒子: Can drop 被吞下的硬币, and makes Swallowed Penny drop two coins instead of one, resulting in infinite money.
- Any Battery type items; see #木制硬币
- Sharp Plug takes only one HP on use.
- 被吞下的硬币 is very powerful as Keeper will always be able to heal himself after taking a hit. However, invincibility after taking damage does not last long enough to pick up the money without risk of death. This can also grant unlimited money, since this will sometimes drop a nickel or a dime.
- If Keeper takes damage from entering a Curse Room, the coin will be dropped on the outside and can't be used to heal before leaving.
- 店主的头 is very useful since enemies will drop coins when hit, which will help Keeper stay alive.
- Piggy Bank works differently with Keeper and doesn't drop coins every time he takes damage.
- 纵火狂 is great with Keeper too, because now you can also heal yourself with all explosions. Combine this with a good bomb item like 神风特攻队, 婴儿博士, 史诗婴儿, 吐根 and you'll be almost immortal.
- Since every heart is changed into flies, items that give extra Heart drops like 瘸子, 病毒, Old Bandage, Fanny Pack, Bloody Penny, Serpent's Kiss, 小查徳 or 遗物 become great sources to generate flies. Having 虫群之心 also helps Keeper deal extra damage to enemies.
- 神圣斗篷 allows Keeper to enter and leave Curse Rooms with less risk.
- Flight is useful in general, and it also lets Keeper enter Curse Rooms with less risk.
- Because of Keeper's slow rate of fire, any Tears Up items are a boon to him. His tears stat can be raised higher than the normal Inner Eye cap with enough Tears Up. This is because his low Tears stat is actually separate from his triple shot effect, allowing him to hit the standard Tears levels while having triple shots.
- 死猫 and 1up! will allow Keeper to trade all of his health coins in devil deals, reviving him with 1 health coin for Dead Cat and 0 health coins and 1/2 soul heart for 1up. Keeper can later regain lost health coins with health up items.
- Missing Page 2 will activate every time Keeper takes damage, making it an effective replacement to 底片's 死灵书 effect.
- 内眼/突变蜘蛛 cause Keeper's fire rate to drop considerably, but he shoots 6/7 tears in an arc, allowing for greater damage output.
- Blind Rage has good synergy with money-dropping items. Since coins need to complete its animation before you can collect it, the extra invincibility frames gives you a bigger window of opportunity to pick them up.
- Placenta regeneration effect affects the health coins just like regular red hearts and will allow Keeper to regenerate 1 health coin every minute. As Keeper does not benefit from items that trigger at half a red heart, this item has no downsides.
- 科技X synergizes well with Keeper's triple shot.
- Health Ups are useless when Keeper has 2 health coins. However, if a Devil Room opens while the Boss Room item is a Health Up, the player can pay for a 1 Red Heart Devil Deal and then get the Health Up to get back to full health. A XI - Strength card can also be used to get back to two health coins, as the health bonus from the card is permanent for Keeper.
- Devil Deals requiring 2 Red Hearts cannot be taken unless Keeper has a resurrection item, 信用卡,，复视，力量卡或犹大的舌头.
- 全家福，底片和巴比伦娼妇 cannot be triggered by Keeper, since he can't have half a heart of health. An exception is after being revived by Guppy's Collar, which is presumably a bug.
- 圣饼 is actively harmful to Keeper, because it reduces his invincibility frames on hit to half-heart damage without halving the damage taken.
- 圣灵受胎 will not provide Keeper with any familiars, as all heart pickups turn into flies.
- Taking 亚巴顿 will instantly kill Keeper, since it takes away all red health and Keeper cannot make use of the Black Hearts given. Amusingly, it will spawn a lot of flies in the process.
- 嗝屁猫的爪子 will remove a health coin and spawn 9 blue flies. Removing all health coins with Guppy's Paw will not kill Keeper immediately, but he will die upon picking up an item.
- It is not recommended to take 乞丐朋友 or Bumbo as they will pick up coins off the ground that could have been used as health.
- 巨怪的肺 will take a dangerously long time to charge.
- Keeper was publicly revealed to players through an alternate reality game created by the developers, however, files alluding to Keeper's existence already were found after the initial release of Afterbirth. With the conclusion of the ARG, a patch was released to fully add Keeper to the game as a playable character.
- In the games files, there is a character called "Old Man Keeper", which was most likely meant to be the 2nd Afterbirth character instead of Keeper. However, he was replaced with this Keeper. This sprite was later used for April Fool's Day 2016, as Keeper's sprite was changed to this sprite for the day.
- Keeper having two coins instead of hearts for health is likely a reference to the tradition in northern Mediterranean cultures, particularly Greek and Roman cultures, where one would place a coin over each eye of the deceased to pay Charon the ferryman to cross the river Styx. This fits in with Keeper's corpse-like appearance.