# Cards Upgrading & Evolving

<figure><img src="https://1006617620-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FrQPJiqrAYBJOE50JKCjZ%2Fuploads%2FE3nmJXemGpivj7MUoBw5%2FCard_Level_Up_%26_Fuse_mid.gif?alt=media&#x26;token=d4155fe4-1d6e-4b7f-a1ed-5a208b5f4ebb" alt="" width="335"><figcaption><p>Card Upgrading and Evolving by Fusion</p></figcaption></figure>

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.