I thought I would be making this deck for the fun of it (and to warm myself back up to homebrewing). What I forgot about was that the 250th YCS was going on the week I was recording the video, and the fact that Kashtira has peaked into the metagame. What I also just noticed is that Dark Magician (the archetype) can also work well with the Kashtira cards as an extra step towards XYZ extensions. Even without one or the other, both can hold their own in their own way as I had experimented this week.
For the Dark Magician package, I went with the Dragoon package to feed off of "Eternal Soul" and "Dark Magical Circle". All by milling "Dark Magician" from the deck and Special summoning him next turn with "Eternal Soul" (triggering the effect of "Dark Magical Circle") .I also had the option of adding "Dark Magician The Dragon Knight" to the deck, which is fusion summoned using the spell card "Secrets of Dark Magic". I haven't used this often due to not having a good chance of a "Magician's Rod" nor being able to always play "Timaeus the United Dragon". The XYZ monster, "Ebon Illusion Magician" was used for this deck to special summon "Dark Magician" for Kashtira XYZ extensions.
Kashtira's side of the fence seem pretty rudimentary as always: with "Kashtira Fenrir" and "Kashtira Unicorn" being the centerpieces for search monsters and spells for the archetype; "Kashtira Riseheart" being the miller (and sometimes triggering certain effects of Kashtira spells if banished, such as "Kashtiratheosis"); and Tearlaments/Scareclaw Kashtira being lore pieces that are good for some reason. The XYZ monsters (in my opinion) are what truly make the deck into the siege weapon it was meant to be: from "Dark Armed, The Dragon of Annihilation" and the endless destruction looping (and material feeding for "Kashtira Arise-Heart"), to "Number 89: Diablosis the Mind Hacker" and the Extra Deck cherrypicking with the possible deck destruction on top of it. This alone is what truly proves that regardless of what gets thrown at them (or what ridiculous hybrids Kashtira gets mixed into), they somehow still seem to do just fine. They are just that good at carrying on their own or with another archetype you happen to put them with (within reason).