Do the rules for Combining Game & Spell Effects apply to damage? A player argued that damage wasn't an effect so the rules regarding "Combining Game & Magical Effects" didn't apply. This was in regard to spell damage from multiple Moonbeams cast on different tiles of a large creature where the areas don't overlap.
The following is defined under "Conditions"
Conditions alter a creature's capabilities in a variety of ways and can arise as a result of a spell, a class feature, a monster's attack, or other effect.
If multiple Effects impose the same condition on a creature, each instance of? the condition has its own Duration, but the condition’s Effects don’t get worse. A creature either has a condition or doesn’t.
The following are the rules on Combining Effects.
PHB ("Combining Magical Effects"):
The effects of different spells add together while the durations of those spells overlap. The effects of the same spell cast multiple times don't combine, however. Instead, the most potent effect--such as the highest bonus--from those castings applies while their durations overlap, or the most recent effect applies if the castings are equally potent and their durations overlap.
DMG ("Combining Game Effects"):
Different game features can affect a target at the same time. But when two or more game features have the same name, only the effects of one of them—the most potent one—apply while the durations of the effects overlap. For example, if a target is ignited by a fire elemental’s Fire Form trait, the ongoing fire damage doesn’t increase if the burning target is subjected to that trait again.