> For the complete documentation index, see [llms.txt](https://doc.sololeveling.space/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://doc.sololeveling.space/sololeveling-unlimited/key-features/c2e-collect-to-earn.md).

# C2E (Collect To Earn)

**Solo Leveling: Unlimited** allows you to level up digital collectibles based on the original storyline. The Digital Collectible come in two varieties: **Monster Cards** and **Shadow Army Cards.**

### Monster Cards Rank

* Monster Cards are classified in ranks from E to S.
* Monster Cards can be combined using two cards of the same rank and Essence Stones to obtain a higher-rank monster card.

### Shadow Army Cards Rank

* Shadow Army Cards are classified in **ranks from SB, SA, and SS.**
* Shadow Army Cards can be obtained based on the success rate when upgrading S-rank Monster Cards.

Higher-graded Shadow Army Cards require more effort and Essence Stones to obtain.

### Benefits of Shadow Army Grade

Users who possess a **Shadow Army Grade Monster Card** are entitled to receive weekly Essence Stones as rewards on the SL:U platform. The reward amount increases with the number and level of Shadow Army Grade Monster Cards you possess. As the number of SL:U users increases and the consumption of Essence Stones rises, the reward amount also increases.