Six mana to remove up to three creatures from the game is a steal, even if it leaves behind a few small bodies on your opponents boards
Even if we have a single dragon on board instead, Draconic Lore and Winged Words are just very efficient draw that require little setup
The idea is to Blood Artist people out with Zulaport Cutthroat and Wayward Disciple, but Pious Evangel makes me want to try to staple a Demonic Pact engine in, and Angelic Purge is a reasonable fit anyway
If you flip a second Illuna, you can add it to hand and then mutate it onto the first one for a double trigger (and no legend rule!) Its harder to see exactly what to do with Vadrok, Apex of Thunder , since one of the best spells in Jeskai to recast Deafening Clarion will also kill Vadrok unless you mutate it under something with better stats
For a little peek into why Monastery Mentor was restricted in Vintage, we have only to examine the EU Vintage Championships before it was hammered
For casual play, tokens and emblems are some of the best things to proxy because they improve board clarity