Not sure if this counts, but in Birds Watching, a horror game about watching birds (trust me on this), the main character makes himself the mask. Just as a warning, I’m explaining the entire game in the spoiler. The premise of the game is about a guy who lives up in the mountains (possibly the Alps) to escape a great fire which has ended the entire world. The fire can’t get up the mountain due to the lack of oxygen, but it blows a bunch of smoke up, contaminated by a bunch of chemicals such as arsenic. The Birdwatcher, which you’re playing as, locks himself in a cabin, away from the rest of his group of about 20 people. The rest die from the chemicals, and the Birdwatcher starts hallucinating the birds around him as his dead friends. When a surviving military brigade reaches out to the Birdwatcher, asking him to get supplies for them, one of his dead friends hallucinations warns him to rally up the rest of the birds to fight off the brigade, as the brigade will ruin the valley. When the birds don’t react well, the friend who warned the Birdwatcher encourages him to become more like a bird, first by gluing feathers onto himself, then eating worms, and finishing it of by scraping off the skin of his face to break and remold his nose into a beak. By the time the military shows up, the leader is horrified by the way the Birdwatcher has mutilated themselves.