> For the complete documentation index, see [llms.txt](https://secondearth.gitbook.io/en/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://secondearth.gitbook.io/en/play/strengthen.md).

# Strengthen

The paid service provided by the Earth Alliance allows some NFTs and equipment to be upgraded to higher quality, with a certain failure rate, and a certain probability of disappearing when fail.