Simple RAW for 5e V: The Disadvantage Strikes Back

[E’Tallitnics]

Q100

Is this a correct statement per RAW?

When a creature is invisible (in combat) and has not taken the hide action their location is known even if they are in an area of silence, not moving, & have somehow done away with their scent somehow (maybe via wish).

Attacks on them have disadvantage & they cannot be targeted by spells/effects that require the target to be seen.

The reason I ask is because in Dungeon of the Mad Mage a section reads:

"Halaster remains invisible even while attacking or casting spells....[H]e then uses the power of the throne to throw his voice so that he doesn't betray his location when he speaks..."

A100: Yes. Being invisible is not hidden. A Stealth check must be processed to generate a DC for a contested skill check.

The rest of your 1st paragraph removes some of the other ways you might detect an invisible creature. Your 2nd paragraph is 100% correct.