The Flash method of detecting invisible creatures -- does it work?

[Noumenon]

There's an invisible creature in the room, and the Flash has no way to see it, and no time to follow the 3.5 rule about making melee touch attacks into two adjacent squares at a time. So he quickly runs back and forth through all the squares in the room at 100 mph. When he bumps into the creature, he takes his standard action and attacks.

This is an exaggeration of my real question, which is, "If I have a huge invisible Efreeti in a room and somebody moves through three of his squares, or worse, stops in his square, does he detect the Efreeti? Should I roll melee touch attacks behind the screen, or rule that the efreeti is avoiding an overrun attempt? And when the efreeti eventually appears (possibly to do an AoO), how do I deal with them sharing a square?"

 

[Axel]

If the Efreeti is inclined to attack the person, it gets an AoO as soon as someone moves out of a square it threatens. Given it's a huge creature this should be well before someone walks into it.

If it declines to attack, invent something. That's why you're a DM and not a player... Something like a Dex check, or relfex save to avoid being walked into. Otherwise the PC is aware that something invisible is in front of it. If the PC is running, maybe they both get a trip attack against each other (like running into an invisible wall).

 

[Dandu]

You are a disgusting pervert and should be ashamed of yourse- oh.

Uh, it'd probably work.

 

[Noumenon]

It just seems so much more effective than all the DMG-approved ways of detecting invisibility (20+ Listen DCs, 40+ spot DCs, checking two squares a round with a touch attack...)

 

[frankthedm]

This is an exaggeration of my real question, which is, "If I have a huge invisible Efreeti in a room and somebody moves through three of his squares, or worse, stops in his square, does he detect the Efreeti? "

Not necessarily. Creatures don't take up 100% of their base size.

I'd rule the Efreeti can chose to let the person moving through their space.

If they stop in the Efreeti's space, I'd give the Efreeti the option of being Squeezing and flat footed until someone left that space in question.

 

[Greenfield]

Okay, so the Barbarian/Monk with the Boots of Speed, er, I mean the Flash decides to move through all the squares in the room to try and bump into the Invisible creature.

If the invisible foe takes up one square, he gets a touch attack roll, and has the same 50/50 miss chance as any attack made against an invisible creature. Miss the Touch, no contact. Miss the 50/50? No contact.

That's just how the rules work, presuming that said critter is trying to avoid contact. So it has a less than 50% success rate, but a better than 100% chance of allowing the opponent an Attack of Opportunity (as high as 900%, if the opponent isn't against a wall, or in a corner.). That is, one 100% chance for each square the critter threatens, including the one he's standing in.

 

[Loren Pechtel]

In general I would always allow the invisible creature to simply step out of the way. I would only disallow that if there was no suitable location to step to.

If someone is actively trying to find the invisible creature and isn't using a shield I would let them spread their arms and thus hit anything within their 5' square (or whatever their facing in the direction of movement if they aren't of standard size.) Thus if the guy is hiding in a 5' corridor he's going to be found, squeezing doesn't apply.

However, I would allow anything bigger than 5' to squeeze themselves into a space 5' less than their normal size unless they were something oddball that was inflexible. (A rolling beastie from a sci-fi story comes to mind. A ball, no limbs, it attacked by rolling over what it wanted to eat.)

 

[kitcik]

The Flash method of detecting invisible creatures -- does it work?

Only if they whistle (or scream)...

 

[howandwhy99]

Whatever your solution, think of from both PC and NPC points of view.

If the invisible 16-square enemy is run through by the PCs, are they going to hit it?

If the invisible 1-square PC Thief is run through by a 16-square centipede, can the PC choose to avoid?

PCs let other friendly PCs through their spaces all the time. Avoiding an enemy entering your square is possible too.

in 3.x perhaps its a grapple attack or overrun attack with the defender having full concealment bonuses.

 

[Greenfield]

Whatever your solution, think of from both PC and NPC points of view.

If the invisible 16-square enemy is run through by the PCs, are they going to hit it?

If the invisible 1-square PC Thief is run through by a 16-square centipede, can the PC choose to avoid?

PCs let other friendly PCs through their spaces all the time. Avoiding an enemy entering your square is possible too.

in 3.x perhaps its a grapple attack or overrun attack with the defender having full concealment bonuses.

How about calling it a simple Touch attack, with the defender having full concealment (i.e. a 50% miss chance)?