Official Quakewiki Video - Quake - E4M4 - the Palace of Hate
Another level to be more irritating for the 100% completionist. An exclusive trap called the Guillotine can be a challenge to pass without taking damage (You have to quickly back up before it descends and run through as it rises a few seconds later), a nearby secret is extremely useful in this circumstance as it bypasses the trap. However, springing the trap and taking the damage also summons four Fiends (Hard has two) meaning completionists will likely have to take the damage. Of course, I discover during this video that using the Ring of Invisibility and going under the trap will result in the Fiends not spawning, they have to detect you to spawn. Beyond this portion, it is fighting a nearly never ending wave of Fiends.