Lanefan
Victoria Rules
The answer to the first question depends greatly on what the specific PCs can bring to bear on the situation. What they in fact did, after simple observation revealed nothing other than some timing elements, was summon two sets of creatures (3 summoned monsters [giant toads] and 3 summoned warriors) and sent them down there. Watching what happened to those creatures told them that there were a variety of possible effects, that not all the effects were deadly, that one of the effects was paralysis or stun, one generated an acidic web in that segment of the room, and that one summoned a Giant to defend the crystal. They also managed to connect some colours to their effects, enough to realize that the effect for each colour seemed to be consistent e.g. a green flash always summoned a Giant if there was anyone or anything threatening the crystal at the time.I can't speak for others, but what I want is clear stakes. I want to know what I'm risking, what the potential rewards are, and how the rules of the game work in this situation. If @Lanefan tells me I am going to have to figure out what the rays do, that's fine. What are the ways to do that, and what are the benefits and risks of each strategy.
The answer to the second question may or may not become apparent until after some trial and error.
Oh, and in case it matters, they had very strong reason to believe their overall goal was removal and-or destruction of the flashing gem.
Those sort of things (bolded) are IMO fine if used quite sparingly as a twist or unexpected consequence. Any more frequent than that, and yeah, it's not much fun.What I don't want is a ton of long tedious low stakes prefatory play that could be elided. I don't want situations where I do the thing and some completely unknown factor is suddenly injected into play which snatches victory from my hands, or turns one level of risk/consequences into something different.