Burn self script suggested by amongus

-- LocalScript (put in StarterPlayerScripts or StarterCharacterScripts)

local Players = game:GetService("Players")
local player = Players.LocalPlayer

local function burnUntilDeath(character)
	local humanoid = character:WaitForChild("Humanoid")
	local rootPart = character:WaitForChild("HumanoidRootPart")

	-- Add fire effect
	local fire = Instance.new("Fire")
	fire.Heat = 10
	fire.Size = 8
	fire.Color = Color3.new(1, 0.4, 0)
	fire.SecondaryColor = Color3.new(1, 0, 0)
	fire.Parent = rootPart

	-- Constant fake damage until dead
	while humanoid.Health > 0 do
		humanoid.Health = humanoid.Health - 2 -- again, only local
		wait(0.2)
	end

	-- Clean up fire after death
	fire:Destroy()
end

-- Run when player character spawns
player.CharacterAdded:Connect(function(character)
	wait(1) -- Let the character fully load
	burnUntilDeath(character)
end)

-- If already spawned
if player.Character then
	burnUntilDeath(player.Character)
end