How do spells cast using the Innate Spellcasting trait interact with a Rakshasa's Limited Magic Immunity trait?

Question

If a creature with Innate Spellcasting tries to use an innate spell against a Rakshasa, how does it interact with their Limited Magic Immunity trait?

Limited Magic Immunity. The rakshasa can't be affected or detected by spells of 6th level or lower unless it wishes to be. It has advantage on saving throws against all other spells and magical effects.

Do innate spells have a level?

Answer 1

Innate Spellcasting uses Base Spell Level

In the monster manual it states this about spells cast with innate spellcasting:

Unless noted otherwise, an innate spell of 1st level or higher is always cast at its lowest possible level and can’t be cast at a higher level

So, unless the spell cast's base level is level 7 or higher, the Rakshasa's ability would affect spells cast using innate casting

Answer 2

The Rakshasa interacts with innate spells as normal

Innate spells are normal spells, so if the spell is of 6th level or lower, the Rakshasa can't be affected or detected unless it wants to be. It also has advantage on saving throws against the spell.

The spells level is listed in the spell description, or is explicitly stated

For example, Drow Mages have the following innate spells:

Innate Spellcasting. The drow’s innate spellcasting ability is Charisma (spell save DC 12). It can innately cast the following spells, requiring no material components:

At will: dancing lights

1/day each: darkness, faerie fire, levitate (self only)

View the individual spell descriptions for each spell to see their levels.

• Dancing lights is a cantrip, which means it is level 0
• Darkness is level 2
• Faerie Fire is level 1
• Levitate is level 2

The same is true for PCs

For example, Tiefling's Infernal Legacy states:

You know the thaumaturgy cantrip. When you reach 3rd level, you can cast the hellish rebuke spell as a 2nd-level spell once with this trait and regain the ability to do so when you finish a long rest. When you reach 5th level, you can cast the darkness spell once with this trait and regain the ability to do so when you finish a long rest.

• In this case you can cast thaumaturgy, which is a cantrip (level 0).
• Hellish Rebuke is level 2.
• You can cast Darkness, which is level 2.

Answer 3

Yes, innate spells have a level and they interact with a Rakshasa's Limited Magic Immunity the same way as other spells.

From page 10 of the Monster Manual:

Unless noted otherwise, an innate spell of 1st level or higher is always cast at its lowest possible level and can't be cast at a higher level.