An Invitation

Welcome to Tesifa Park!

You've recieved a letter. It's in an envelope that's been embossed with shiny teal-mint ink designs.
"Greetings! You are cordially invited to an exclusive Ultimates only meeting at Tesifa Park! Thousands of Ultimates will be in attendance to ride rides and stay in our 5-star luxury resort! Free of charge (relatively). We hope to see you there! ♡"
There's an address, although no signature. Who sent this?

This killing game is based off of a Discord killing game run by myself and participated in by some of my close friends! Please enjoy our dumbass endevours!