I know that Rakshasa can't be affected by spells of 6th level or lower … but does that apply to spell with verbal components, or in a case where it does thunder damage?
Best Answer
The Rakshasa stat block has this property:
Limited Magic Immunity. The rakshasa is immune to spells of 6th level
or lower unless it wishes to be affected. It has the advantage of saving
throws against all other spells and magical effects.
The spell Silence is written like this:
Silence
2nd-level illusion (ritual)
Since Silence is a 2nd level spell, so the Rakshasa is immune to its effects.
The Rakshasa is immune to the spell, therefore, he can still use spells with verbal components, speak and do anything to make sound, including thunder. However, the spell silence states:
Any creature or object entirely inside the sphere is immune to thunder damage,
The creature itself is affected not the Rakshasa, so the Rakshasa can cast a spell with thunder damage, but any creature within the sphere of silence is immune to the damage and so will not take the damage.
There's nothing RAW that indicates that players would know whether or not a creature is affected by most spells, though presumably in the instance of Ray of Sickness, players could infer whether the spell had taken effect based on a creature's behavior.
Does the hobgoblin captain slump for a moment, resting on her spear? Does the shadow demon react at all to the beam? Those are probably telling.
Zone of Truth appears to be a little different since the caster explicitly knows whether the target succeeded or failed the saving throw, which can only occur if the creature is affected by the spell in the first place; a creature which isn't affected by the spell never makes a saving throw. In this way, the caster would know if the hostage weren't affected, if only circumstantially; instead of having succeeded or failed to resist the spell, the Rakshasa would effectively be invisible to the spell, which would surely be suspicious.
Best Answer
The Rakshasa stat block has this property:
The spell Silence is written like this:
Since Silence is a 2nd level spell, so the Rakshasa is immune to its effects.
The Rakshasa is immune to the spell, therefore, he can still use spells with verbal components, speak and do anything to make sound, including thunder. However, the spell silence states:
The creature itself is affected not the Rakshasa, so the Rakshasa can cast a spell with thunder damage, but any creature within the sphere of silence is immune to the damage and so will not take the damage.