Ok, invisibility has always had its limitations. Powder on the floor, dogs and dragons could smell you, enemies could hear you, etc. But there is a section on pg. 60 of the 1E DMG that shows a chart for the possibility of detecting invisible creatures/characters based on HD and INT.
Once you hit the low teen levels and with an INT at the higher end of the scale, invisibilty becomes nearly useless! Consider:
11th level/10+ to 11 HD with a 15-16 INT gives a 30% chance to detect invisible beings.
13th level/12+ to 13 HD with 51-16 INT gives a 50% chance to detect invisible beings. With a 17 INT it rises to 55%.
15th level/15+ HD with a 15-16 INT gives an 85% chance to detect invisible beings, with a 95% chance for INT 17!
So once that wizard hits 15th level, if he has a 17 INT he can detect invisible creatures 95% of the time. That's unreal! Even with a mere 15-16 INT (and I rarely see wizards with lower INT scores), he has an 85% chance to detect any invisible creatures.
By "detect", they mean just that...they somehow see a shimmer or something that lets them know something/someone invisible is there. This is without any need to hear, smell, or sprinkle flour on the floor.
I think the chart gets a little too generous at higher levels. For example, at 13th level, with even an average INT of 11-12, there's a 55% chance to detect invisible beings.
Seems to me that invisibility becomes much less useful at higher levels using that chart.
What do the rest of you think?
