Mercure’s Lab Guide for Seven Knights Re:Birth. See how to unlock Mercure’s Lab, Dark Predictions, Black Magic Experimentations, Hero Forecasts, Slot Rates, and Leah in 7K ReBirth.
Table of Contents
How To Unlock Mercure’s Lab
Clear Adventure Nightmare 5-30
Mercure’s Lab unlocks after clearing Nightmare Chapter 5 Stage 30 in Adventure mode. Unlocking the Lab serves as a reward for progressing through the more challenging Nightmare content.
Nightmare Mode Guide & TipsCan Be Accessed in the Workshop
Mercure’s Lab can be accessed through the Main Menu → Workshop → Mercure’s Lab tab once it has been unlocked by clearing Adventure NM 5-30. This tab becomes available in the Workshop menu after completing the required stage and allows you to begin hero experiments.
Mercure’s Lab Uses
Unlock New Heroes
Mercure’s Lab is especially useful for players aiming to complete their Hero Codex. By sacrificing unused or duplicate 6★ heroes, you can obtain new heroes that you may not have unlocked through regular summoning.
Fill Up Hero Codex
Since the results from the Dark Predictions often include a wide range of heroes, including those that are harder to obtain. It increases your chances of discovering missing entries in your Codex, helping you earn Rubies.
Expand Your Roster
Mercure’s Lab helps you grow and improve your hero collection by letting you trade in weaker or duplicate heroes for new, stronger ones. This way, you can keep upgrading your team by getting rid of heroes you don’t need and making space for better heroes. It’s a great tool to keep your roster strong and ready for tougher challenges as you play.
List of All HeroesHow Mercure’s Lab Works
- Material Selection
- Dark Predictions
- Black Magic Experimentation Results
Material Selection
When selecting materials, players can choose up to five 6-star heroes and Leah to use as materials. The choice of hero materials is important, as each hero used contributes to your overall score based on their value and type. Using higher-quality heroes will result in more points, helping you achieve a higher rank.
Rank Up GuideSome Heroes Cannot Be Selected
Not all heroes are eligible for use in Material Selection. Specifically, heroes categorized under the Seven Knights of Old cannot be added as material.
Substitute Leah as Material
Leah can be used as a material in place of a standard hero, providing greater flexibility when forming your material combinations. Including Leah in your material lineup gives you more room to strategize, optimize your score, and explore various possibilities without compromising your main roster.
Quality‑of‑Life Improvements
After the recent update, a filter function has been added to the material selection screen. It allows you to exclude heroes who have completed Transcendence, are equipped with gear, or have been powered up. This helps prevent accidental selection of valuable or prepared heroes.
Latest News and UpdatesDark Predictions
Dark Predictions let you see which hero you might get. Only one hero from the list can be chosen. You can use Predict Again to get a new list, but this will erase the current results.
Hero Forecast
Each prediction costs Gold, and the chances of getting better heroes depend on your rank. The strongest heroes appear in the last slots, so keep predicting if you're aiming for the best.
Slot Rates
The heroes are placed into slots based on their rarity. Higher rarity heroes go into slots with lower chances. Only one Seven Knight of Old can appear at a time. If a Seven Knight of Old is picked, the other heroes are chosen with updated chances.
Check Rate Info
For more details on how heroes are chosen, tap the Rate Info button. It shows the chances for each hero and slot. Keep in mind that the numbers are rounded, so they may not add up to exactly 100%.
Black Magic Experimentation Results
In Black Magic Experimentation, you get one hero from the Dark Predictions. However, take note that any heroes you use as materials will be gone for good. Also, any gear on those heroes will disappear. When you get your hero, all the prediction results will be erased so it's important to choose carefully.
What is Mercure's Lab?
High Risk and Reward System
Mercure’s Lab is a special feature in Seven Knights Rebirth that allows you to sacrifice existing heroes to obtain a new, possibly better hero through a dark experiment. All used heroes and their equipment will be lost permanently.
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▶Back to Top PageRanking Articles
| Ranking Articles | ||
|---|---|---|
 Best Hero Tier List |  Reroll Tier List |  Best Pet Tier List |
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Error Guide and How to FixHero Per Specialty
| By Grade | |||||||||||||||||||
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| Legendary | Rare | Uncommon | Common | ||||||||||||||||
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| 6★ | 5★ | 4★ | 3★ | ||||||||||||||||
| Per Type | |||||||||||||||||||
| Attack | Magic | Defense | Support | Universal | |||||||||||||||
| By Attack-Type | |||||||||||||||||||
| Physical | Magic | ||||||||||||||||||
