I need help with mob spawning through a procedure.

I'm creating a forge mod for Minecraft: Java Edition. It contains a few things, such as a custom boss mob which the player can either encounter WAY too much of in a custom biome in a custom dimension (I'm going to remove that, by the way) or by using a custom boss-summoning item. The thing is, I can't make a spawn egg the result of a crafting recipe. So, I need to make a new item to spawn it. I try to save it, but it gives me this error: Your workspace contains mod elements that don't compile properly. 

Here is the procedure it uses, the message that is said in chat when it is used isn't meant to be any kind of code, I want it to look exactly as displayed, and I want the mob to spawn a few blocks ahead of the player.