Can I cast darkness on an object, then turn it off and on during a round of combat?

Question

I'm playing as a shadow monk in my 5e game. I have the same question about darkness that I have seen. What is the usefulness? My struggle is that they have given darkness to a melee character. I assume there has to be a use for it besides setting up teleports 3 levels later.

However, as I was reading it, I noticed that it can be cast on an object and when that object is hidden the darkness goes away.

If the point you choose is on an object you are holding or one that isn't being worn or carried, the darkness emanates from the object and moves with it. Completely covering the source of the darkness with an opaque object, such as a bowl or a helm, blocks the darkness. (PHB p.230)

My question is: Could I cast darkness on a coin in my hand, and close and open my hand during a round of combat so that I can see for my attack and then be cloaked in darkness when my turn is over?

Answer 1

Short answer: Kind of

You can if:

• you have an additional action to spare (uncovering then covering the coin would count as two object interactions).
• your DM thinks a closed fist "completely covers" the coin.

Long answer

The Rules as Written are silent on this exact point, but there are two main rules of relevance here.

Object interactions

The rules for object interactions on PHB 190 are the most obvious ones to apply here - ultimately you are interacting with the coin.

You can also interact with one object or feature of the environment for free, during either your move or your action.

Although this rule is not completely explicit about what "interacting with one object" means, several of the examples given on the same page suggest that this interaction is a one way-process. The clearest examples of this are:

• draw or sheathe a sword
• open or close a door

Furthermore the example of:

• extinguish a small flame

is pretty close to what you are talking about here, and is a one-way process.

So, as far as object interaction rules go, you could either cover or uncover the coin for free, but you would have to use your action to do both on one turn.

"Completely covering"

As the Darkness spell description says:

Completely covering the source of the object with an opaque object, such as a bowl or a helm, blocks the darkness.

So your DM will have to rule if simply enclosing a coin in your hand does the trick. The idea of darkness in D&D is so contrary to physics, that this is a tough one to rule, but your DM might rule that some of the darkness seeps through the gaps between your fingers, your hand is not sufficiently opaque etc.

So...

• If your DM decides enclosing the coin in your hand constitutes "completely covering" and

• If you have an extra action to use on both closing and opening your hand (eg from a class feature)

then you can go with your creative plan. Otherwise you might have to modify it a bit: use your only action but benefit the party, find a more 'darkproof' container etc.

Answer 2

Spend a bit of coin (I would think that if it's more than 10gp, then the DM doesn't like the idea) on having a tailor sew together a pocket that is completely opaque — with a flap to cover the top (using whatever material needed per DM guidance). Have the tailor add the pocket to your vest/tunic. Tuck said coin (or ring, or stone, or whatever) in pocket.

Personally, I like the necklace idea and just tucking it inside the clothing (again, confirm clothing is opaque with DM prior to starting adventure).

The point about interacting with an object as noted above is still in effect though — it's an either-or thing.

A couple levels of Warlock for Devil's Sight would make seeing through said darkness a whole lot easier.