In v11 looking around all item through debug mode, I found a Silvally crest, that gave him +10 to all base stats making him unstoppable. Updating to v12 I still have it but it now says that it gives a different effect for each memory held. Now, this crest can't be equipped, but I think it may actually work because Jan in the changelog says that he had given a lot of new effects. - Silvally Crest now has a ton of Extra Effects. In my playthrough I haven't found it, even in the item