Destroy 1 Pendulum Monster Card you control, and if you do, add 1 "Senet Switch" from your Deck to your hand
Since there are plenty of ways to Special Summon on the opponent's turn, you can utilize both these effects before the opponent's Main Phase even begins, leaving them with only two cards to play with
At first glance, it might seem incompatible with Tenyi monsters or Level 7 Brave monsters that state "can only be special summoned when there are no monsters on the field," but the former does not count Normal Monsters as monsters, and the latter can be special summoned by chaining to the effect of Magicians' Souls, so there is really no problem at all in dealing with Bystials
If you do, banish it when it leaves the field
You can only use each effect of "Fiendsmith's Desirae" once per turn
In Episode 64 it's stated that all those killed, except the Goodwin brothers, have returned to life