Dog Moon
Adventurer
I think you should rename the title of your thread because when I saw it, I immediately thought no, but when I read your first entry, I saw that it was quite different from the title.
No, they cannot challenge a 17th level group, but try to use the atmosphere to mess with the character's heads. Say they're walking through a sewers. Make them hear strange noises coming from around them [This is the Orcs]. Let them see shadowy figures, but try to prevent them from ever seeing the Orcs. Build up mystery. Occasionally have an arrow fired at the group from the darkness from a long range away. It doesn't matter if it hits or not. And if they do manage to kill an Orc, they'll be confused because the Orc was felled in a single hit.
Of course nothing may work against 17th level PCs because height won't matter because most will have fly, Tanglefoot bags will hurt only the Orcs because the PCs will have high enough Reflexes they won't really matter, etc.
No, they cannot challenge a 17th level group, but try to use the atmosphere to mess with the character's heads. Say they're walking through a sewers. Make them hear strange noises coming from around them [This is the Orcs]. Let them see shadowy figures, but try to prevent them from ever seeing the Orcs. Build up mystery. Occasionally have an arrow fired at the group from the darkness from a long range away. It doesn't matter if it hits or not. And if they do manage to kill an Orc, they'll be confused because the Orc was felled in a single hit.
Of course nothing may work against 17th level PCs because height won't matter because most will have fly, Tanglefoot bags will hurt only the Orcs because the PCs will have high enough Reflexes they won't really matter, etc.