This effect allows you to choose between playing a Tamer card with [Tai Kamiya] or [Kari Kamiya] in its name from your hand without paying the cost or hatching a Digi-Egg in your breeding area
So in a way, if you opened the box and the cat in this experiment is dead, YOU by opening the box and observing its contents, are responsible for the cat's death
Over time, this approach overwhelms defensive boards without relying on combos, which is why Aurelia often appears in discussions around top MTG cards for combat-focused Commander decks
Shoutout to Spikefield Hazard for hitting players and exiling, both relevant lines of text, Song-Mad Treachery in general (It mostly doesn't matter how much a given threaten effect costs, as on a good day it'll be the last spell you cast), and Malakir Rebirth/Sejiri Shelter for being great at the low threat count decks (prowess) that I love encouraging
No matter which way you look at it, not that anyone should, this thing is creepy through and through
If you run a mono-black deck, sometimes you need to make do with what youre given and not look the gift horse in the mouth