Scott Way's page

I have a group that has been playing for over a year and is now getting close to the end of the campaign. And as they are all getting into higher levels they are abusing certain spells Greater invisibility is the worst one.
How do I as the DM make a game a challenge for them if i cant see them to effect them. With out making it look like Im "Trying to Kill" the players. Since not all encounters will have creatures with clerical abilities to Purge it or casters with true seeing even creatures with high sent abilities still will have a high miss chance. Tremor sense doesn't work since they piggy back fly on to there greater invisibility.

Does anyone else see the flaw in the duration of Greater Invisibility? Or have a possible solution that isn't going to make it appear that Im picking on certain players?

During the spell, you inscribe runes around a single square of space. All creatures and objects within that square at the conclusion of the casting of this spell are instantly transferred to a temporary extradimensional space in which time does not pass. Creatures or objects that are only partially within the space are not transferred. Once the spell ends, the extradimensional space disappears, and any creatures or objects in the extradimensional space appear in the nearest unoccupied space to the original square exactly the same as when they left. You cannot dismiss this spell once it has been cast.

My Question here is the spell lasts for 6 hours/lvl is inside the shelter or outside time? If outside time how "time" would you have inside and vise versa ie does the space last for 6 hours/lvl and a minute of real time pass?