Does a huge invisible creature grant invisibility to the target behind it, blocking the line of sight of the target in front of it?

Question

Does a huge invisible creature grant invisibility to the target behind it, blocking the line of sight of the target in front of it?

Would a tiny creature occupying the space of a huge invisible creature also be invisible?

Can the tiny creature enter the huge creature's mouth and benefit from invisibility? What are the implications of a tiny creature being in the mouth of a huge friendly creature, and are opening and closing the mouth actions?

Answer 1

The Invisible condition applies only to the invisible creature itself.

The rules language in the Invisible condition (and similarly the Invisibility spell) indicate that only the invisible creature itself is invisible, not other creatures affected by the creature.

From the Invisible condition:

While invisible, you can't be seen. You're undetected to everyone.

There's no indication that other creatures are also affected by the invisibility, unless the effect is making those creatures have the Invisible condition as well (ex. both are behind an Invisibility Curtain).

With this context, here are the answers to the questions (in order). The first two questions have clear answers in the rules:

• A huge invisible creature doesn't make creatures behind it invisible. They would provide Standard cover to the creature behind them (see Cover rules). As a GM, I would rule that if the Huge creature's cover bonus is the sole reason that an attack was a failure, and the Huge creature was Undetected, they'd become Hidden instead of Undetected. However, there's no clear rules interaction for this particular case.
• A tiny creature occupying the same space as a Huge invisible creature is still visible. The tiny creature would have Standard cover.

The final two questions do not have clear answers, and would require a GM ruling:

• Unless the Huge creature is using Swallow Whole, there's no rules text regarding one creature hiding in another creature's mouth. This could perhaps be ruled as using the Take Cover action if it's hostile or indifferent, or perhaps riding (see "Riding PCs" text) the larger creature if it's friendly. While I would rule that the tiny creature is invisible in this case (in a manner similar to the invisible creature's equipment being invisible), this would require an individual GM ruling.
• As with the previous question, there's no clear rules for this interaction. If both parties are Friendly to each other and agree to this plan, the clearest ruling would be to treat this as the tiny creature riding the huge creature, meaning both creatures would lose one of their actions each turn. If the tiny creature is attempting this maneuver with a Hostile huge creature, the tiny creature would effectively be inflicting the Grabbed condition on themselves.

Answer 2

Invisibility only makes the creature itself invisible

Think about it, if you could not see what is behind the invisible creature, it would not be invisible, would it?

The invisible condition states:

A creature with the invisible condition (by way of an invisibility spell or invisibility potion, for example) is automatically undetected to any creatures relying on sight as their only precise sense. Precise senses other than sight ignore the invisible condition.

It does not affect other creatures around or behind or under it. If the creature would swallow or enclose another creature, that creature probably would be invisible too, like the worn or carried equipment of the creature is assumed ot be invisible, or invisibility would not be of much use.