Plugin plugin = Main.getPlugin(Main.class); Location hd = new Location(world, 527, 48, -954); Hologram display = HologramsAPI.createHologram(plugin, hd); TextLine t = display.appendTextLine("The core is big!");

I wrote this up, no hologram shows, says local variable t isn't used, wiki doesn't explain anything.

You didn't create a hologram with text, just the text line. Need to add the text line to the hologram.