First off, I'm new to the subreddit and new to reddit in general, so hello!

When I say 'cryptic' I mean when the player needs to decipher a game mechanic or any part of a game by themselves usually through experimentation. Some games are more cryptic than others. Adding cryptic features to a roguelike (or any game) is risky, because you risk players never fully understanding your game.

Less cryptic The Binding of Isaac is a pretty easy example. You find an item, and can guess what it does by how it looks. When you pick it up, you are shown the name of the item and a short description. You player often will change, which gives more hints as to what the item does. You can assume that the X-ray vision item will allow you to see something you wouldn't normally be able to see based on it's looks. After you pick it up, you'll eventually see that it opens secret rooms automatically, and the player puts two and two together.

More cryptic Now we'll look at 868-HACK (or any Michael Brough game, really). This game removes the visual clue of what an item (program) does and the player has to rely on the name of the program and the also cryptic descriptions. DEBUG is probably the best example, as it's the hardest program to understand (in my opinion). The name doesn't help at all, and although the description does help decipher it, few people will instantly understand what it does: destroys overlapping. This is a weird one because 'destroy overlapping' is a pretty situational ability, and it only lets you use it when it actually does something. Some players will die without ever getting to use the program, and might be afraid to try using it again.

Potentially too cryptic For the last Ludum Dare, I made a roguelike called Nine till Void which I wanted to be as simplistic as possible in gameplay while being as cryptic as possible in understanding it. It's a game where every action is done using items which are strewn out on a 9*9 board. Items have symbols that have no relation to what they do, they don't have names, and they don't have descriptions. So it's all up to the player to experiment and figure out what they do. No clues. Some are more obvious than others such as one that shoots a laser in the four cardinal directions or one that lets you move 4 spaces but spawns an enemy at a random location. Then there are the ones that aren't easy to understand. One destroys enemy bombs or fire trails. If you use it when no fire trails or bombs exist, it does nothing. Another adds 3 ticks to the timer which ticks down once each turn. When it hits 0, the level starts to collapse, and you have to leave, or risk death (my take on the Spelunky ghost). The problem is that the timer is also never explained, and the player has to figure out what it's purpose is and how to interact with it. If the player doesn't know how the timer works when they use it, chances are they won't even know what the item does, and will avoid it in the future.

For reference, here's what the game looks like. I should also explain that I'm almost finished with a post-jam version of the game which has a tutorial that explains all of the important mechanics, but leaves the items a mystery.

So, where do you have to draw the line? Or should a line even be drawn?