Hi there 
When reading up on enchantments (a friend of mine wanna play wizard and asked for help on schools) i noticed that charmed npcs know they've been charmed afterwards. (which the school of enchantments counter)
But do targets (lets say a guard) that have been enchantet by sleep, know that they've been enchantet? (if they live to tell the tale)
If it's reasonable, they will know that something is odd. If one single person sleeps while making nightwatch, the person might think that he doozed off. If a whole crew is sleeping, then they will definitely think that it muste be because of magic.
So in the end you have to look at the context. ;)
Description of magic says people dont automatically know they are affected by magic, unless the spell has visible effects or specifically says the targets are aware. Most of the charm spells specifically say the target knows it was charmed.
I agree that victims of sleep don't automatically know it's because of a spell. But they can deduce it from context. If the last thing the sleeper saw was a man in robes walking towards him waving his hands in arcane patterns, he'll be able to find out that man cast a spell on him. If a guard and his three mates all fall asleep at the same time, they can deduce that it wasn't natural sleep, and was probably caused by a spell. If the guard fell asleep and woke up in a broomcloset locked from the outside, probably wizard.
Then again "a wizard did it" is probably the most used excuse in a city where everyone at least has heard stories about spells common to spellcasters. Fell asleep during your guard? "a wizard must have cast a sleeping spell on me." Caught stealing? "I wasn't me. It must have been an invisible wizard". Caught with another man's wife? "A wizard must have charmed me."
This also makes it the single most heard excuse. A guard captain will probably believe a lone guard slacking off and napping more believable than him being the victim of a sleep spell.
Given that sleep has a verbal component, I guess that in most situations you would realize someone cast a spell on you (even if the wizard had left his robes at home that day )
jaelis wrote:
posineg wrote:
I have ruled that spell casters can attempt to obfuscate their spells, but doing so carries added risk.
Somatic/Material: sleight of hand vs. Passive perception.
Verbal - deception vs passive insight.
1st-2nd level spells - no penalty but failure imposes disadvantage on further checks against the same target(s) and disadvantage on charisma checks made to positively influence.
3rd-5th: disadvantage on your check.
6th-9th: spells to complex to cast deceptively. No check allowed.
I agree with the others that it sort of relies on context.
If a character (PC or NPC) is sleep deprived, has eaten a large meal, has drinken a little too much, or is bored and alone, then it's easy to say that falling asleep could be a natural consequence.
If a character has had normal sleep and is not intoxicated, then waking up on the floor or on the ground in the middle of the day is going to be a dead giveaway that someone has sleeped them if they are aware that a sleep spell exists. Even if they don't know that a sleep spell exists, in a world where magic is accepted as a reality (even if it's rare for average people to see it) it's easy to surmise that magic could do that.
Of course, they might also think it was some kind of poison. However, that gets less likely when more people are sleeped.
MechaPilot wrote: