This is a simple, somewhat compact device that makes a boss battle easier to assemble a spawnpoint, item loadout, and boss dialogue.

It uses a frosty lake area, therefore the boss says Welcome to my frosty lair...

Commands that I could have used but decided not to were: /difficulty
/tell
/spawnpoint

The three commands I used were: /say
/give
/effect

To get to the area, there is a button on a command block that you can press to teleport you there, or you can find it yourself