Some background: I want to have the bad guy necromancer have a trap in front of the secret entrance to his lair. He has a small frozen lake that abuts the entrance. To invade, the players would have to walk across delicate ice. Under the ice, the necromancer has concealed a number of skeleton defenders. The entrance is entrapped to activate sliding blocks that will break the ice, giving the characters terrible footing and surrounding them with a horde of enemies.
The problem is that I have a Paladin in the group with Divine Sense:
As an action, you can open your awareness to detect such forces. Until the end of your next turn, you know the location of any celestial, fiend, or undead within 60 feet of you that is not behind total cover. You know the type (celestial, fiend, or undead) of any being whose presence you sense, but not its identity.
I would like to make the ice translucent, so that the PCs can sense that something is down there with a good Perception roll (The skeletons would have the Perception Roll at advantage, due to the PCs being backlit). Would this negate the Divine Sense? Does transparent cover count as cover for this ability? The alternative is to just make the ice opaque, but that would reduce the Creepy Factor™.
The answer to this question has further ramifications: Does DS work through a sheet of thick glass, for instance? Or in a a mirror held around a corner? Could a vampire hide his nature just by standing on the other side of a window?
My first instinct is to say that cover is a game term for something that blocks your ability to target the enemy with an attack, and thus the DS would not work, but if anyone has good compelling arguments one way or another, it might forestall distracting table debate.