Can the Moonbeam spell negate the effect of the Meld into Stone spell?

Question

I was playing a druid in a free-for-all with other players. In a moment of near death and desperation, I cast meld into stone to escape from a paladin to try and heal a bit. Because it was a Battle Royale, the DM had earlier decided that I could only stay in the wall for 1d6 rounds. I rolled a 4, so I could be in there up to 4 rounds.

However, the paladin cast moonbeam on the area I entered from. He argued that as a druid I classified as a shapeshifter and would have a harder time with the spell save. I said that since I was in total cover, I would be unaffected. In the end it was two against one in reasoning, and they decided that I was considered a shapeshifter. So I rolled the save, I failed it, and was expelled from the wall. The DM said I didn't have to take the 6d6 damage from the wall, but I took radiant damage from moonbeam.

Maybe I'm just salty, but the way I have always understood these spells says that should have never worked. Can someone help me to make sure I am corrected if I misunderstand?

Can the moonbeam spell negate the effect of the meld into stone spell?

Answer 1

It is hard to argue that it would expel the druid

Issue 1: total cover

The meld into stone spell does not explicitly say that you gain total cover in the stone, but it implies it heavily. You cannot see the outside, but can move around inside (you can provide somatic components). There is mention of what happens if the stone is harmed, but no mention of the caster gaining any damage resistance or similar, likely due to the assumption that they cannot be targeted. Also

Nothing of your presence remains visible or otherwise detectable by nonmagical senses.

so you are not a statue or relief sticking out of the stone. You are inside it, fully. I think it is a stretch to say that you do not gain total cover while under this spell.

Issue 2: counting as a shapechanger

A pointed out here, druids are not counted as shapechangers. Ruling otherwise would not be terribly unreasonable, but it would be a houserule. (Thanks to Medix2 for the link.)

Issue 3: being forced out of the stone

What the moonbeam spell does is this:

A shapechanger makes its saving throw with disadvantage. If it fails, it also instantly reverts to its original form and can't assume a different form until it leaves the spell's light.

Even if we say that a druid is a shapechanger and thus this section is relevant, the meld into stone spell does not transform them into a new form. It allows you to enter a piece of stone. There is no mention of the caster turning into stone, you remain yourself.

Conclusion

While there are arguments against all 3 issues, all are pretty weak. I do believe that by a reasonable ruling what you described should not happen. However, please consider that the DM likely had to make a ruling on the spot to keep the action going. If you do not have the time to read through the spells meticulously, there is a certain logic in ruling in favor of moonbeam. Please keep this in mind if you plan to bring this up with your DM.