To cast a fused split spell, pay both of its mana costs
Let's take a trip down memory lane and look at the most expensive cards of the Pokemon TCG Sword & Shield era
Ancient Copper Dragon FINAL FANTASY: Through the Ages, Mythic Limited: 2.0 If you hit them with Dragon of Mount Gulg (Ancient Copper Dragon), this likely will win you the game, but thats true of most six-mana cards
While being able to sacrifice for free is great, tutoring is often better
Note: The 3/3 green Boar creature token is also created by Curse of the Swine
Ill say up front that this isnt the most expansive card creation app out there, but its free, its fairly easy to use, and it has enough customization options to satisfy that card design itch