Memories are Items that can be used to change Silvally's forme and type. There are 17 sorts of Memories: 1 for every type with the exception of the Normal type.
For Arceus' forme items, see Plates.
Memories act like Forme-Change Items. When held by a Silvally, it temporarily changes its forms to match the Memory's type. When Silvally is not holding a Memory, it reverts back to its Normal Forme.
After obtaining a Type: Null, Memories can be obtained at the Aether House in exchange for Flawless Gems. Each Memory requires 4 Flawless Gems of the corresponding Memory's type and 1 additional Flawless Normal Gem.