1. Upgrading: Crystals, one of the in-game currency, can level up your cards to increase their power. Card rarity determines the number of levels: common (3 levels), rare (4 levels), epic (5 levels) and legendary (6 levels). Upgrading costs more as the level of a card increases.
2. Fusing: When you have two fully upgraded identical cards, you can fuse them to create a silver card (double-fused card). This one can be further upgraded with crystals. You can then repeat the process, using two fully upgraded silver cards to create a gold card (quad-fused card).
In both ways, card evolution results in increased attack power, greater endurance, enhanced spell potency (single-target spells can turn to multi-target spells), while the speed stat remains unchanged.
---
# Agent Instructions: Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://docs.spellsofgenesis.com/spells-of-genesis/cards/cards-upgrading-and-evolving.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.