So we know that the 4 Hisuian forms and evos shown have something in common, the fact they haven’t appeared in any Sinnoh dex before now, so that got me thinking that we could probably narrow down potential candidates by making a list of which mons either haven’t appeared in a sinnoh dex, haven’t had a regional form before, don’t have an evolution in sinnoh already, and aren’t already a Sinnoh Mon themselves