Theres a solid chance that as Tarkir: Dragonstorm ages, all the Spirit Dragons will go up in price too, making it a solid future investment
Theyre often red creatures, black creatures, blue creatures, or some combination therein
Once you have a Solosis, Vulpix and Sneasel (Ditto Prism Star can substitute for either of the latter), and you fear that your opponent will KO one of them, then Ditto is the perfect backup
Infinitrack Fortress Megaclops also has a nasty stealing effect, allowing you to bring an XYZ monster back from your graveyard and use one of your opponents monsters as material for it
By letting you activate each of your walkers an extra time, it doubles loyalty gains and quickly pushes them toward ultimates