The phrase "holds everything" can be replaced with a number of different synonyms that convey the same idea. For instance, you might say that a container "stores everything" or "houses everything." Alternatively, you could say that something "contains everything" or "comprises everything." Another possibility might be to use the phrase "holds all" or "holds the entirety of." Finally, you could use the word "holds" followed by a specific adjective that indicates the comprehensiveness of the object in question, as in "holds complete" or "holds total." Whatever synonym you choose, the important thing is to convey the sense that the object is capable of holding or containing everything that it needs to.