This 30 year old adventure / RPG is brutal, quite difficult, and its (solo!) creator must have a huge fan of the 1977 Mexican nunsploitation horror movie Alucarda. The movie is a retelling of Le Fanu's seminal work of Gothic/Vampire Horror Carmilla—the book is well worth your time; subverting the Victorian gender stereotypes that ultimately undergird most vampire horror... but I digress. This is about a 1994 adventure game that promises to be "Too Evil For Those Under 13"! There's a sexy, serious looking witch on the title screen! The internet only preserves the "shareware" version of the game, but it appears to be fairly complete. The full game promises "more art and more sound" but you can play through a full story cycle with just the shareware... and I doubt you can mail $15 to the address listed and get the full game 30 years later...
So... is it "Too Evil"?
You play "Alucarda", the daughter of a woman recently condemned—rightly, it would seem?—as a witch and burned at the stake. Her mother appears to her and demands that she take vengeance. Alucarda wears black robes, enjoys shiny silver daggers, and has already, by the time the story starts, collected a formidable array of satanic and witchy paraphernalia, including a throne that I think I saw on a couple of black metal album covers. The gameplay is mostly straightforward—if difficult to control—that black robe ensemble sure seems to inhibit Alucarda's mobility to an annoying extent. You click around on anything that seems promising, and on screen your avatar shuffles vaguely towards the cursor, looks at things, reads spellbooks, and picks things up. Sometimes you encounter a character and choose a dialogue option. Sometimes they just wanna fight you in a turn-based slapping contest that is seemingly impossible to win without having the proper item[]. If you click around just so, you might happen across a needlessly bloody sheep carcass or a coffin, either of which you raid for parts. Parts you'll use to craft spells at your cauldron, naturally. I never really found anything else to do with them, certainly. Ultimately, you have to find the right graveyard, travel to hell, and fight the devil himself[], proving that perhaps the game isn't evil so much as grimly lurid.
If you're familiar with the "edgy" and "brutal" setting of Lamentations of the Flame Princess, a tabletop RPG loosely inspired by a doom-and-grime-and-everyone-sucks mentality in a Thirty Years War-ish historical setting, then you'll grasp Plague's ambience immediately. The town[] here has a germanic-looking execution and torture field, with well-used stakes, wheels, and scaffolds. A lovely little hamlet to visit while road-tripping! There are more witches in the woods, a portal to a shadow realm, ruins you can explore (or at least click on things in), a church with a fearful priest, and a nunnery full of weirdoes (that I think is supposed to have a logic puzzle to solve?) wherein one of the nuns—the young cute one whose name references the aforementioned movie and book—is evil and might have been behind the wave of persecutions and torture (it was hard to say, I kept accidentally skipping dialogue). The game's story is schlock exploitation of gothic horror themes and never really brings itself to commit to anything besides "heavy metal album cover."
So... is it too evil for under-13s? I'd say it's "needlessly grimy and exploitative", macabre, trashy, and definitely "Too Punishing And Obscure" for the under-13 set, though a walkthrough is available should you get stuck and/or lose the thread of what you're supposed to be doing.
I rate it a C-. If I'd spent any more than a couple hours with it, I would have regretted it. Your time is probably better spent with le Fanu and Carmilla, and maybe that old Mexican horror flick. I'm given to understand Guillermo del Toro's a fan.
[]: I got killed by the town guard over and over again until I figured out there was another direction to head in.
[]: "Yeah, I met the devil, and I beat him in a turn-based slapping contest. I cheated using magic, but you'd think he have thought of that."
[]: The only townsfolk you see immediately flee your presence, having decried you as a witch. Maybe the getup is just a little much, ma'am?