Fantasy games has vermin of all sizes. Rats the size of dogs in dungeons, man-sized spiders in the forests catching halflings in their webs, and of course the lowly rot grub. However, these creatures are rarely used to full effect in role-playing. Here are a few thoughts on a few dirty tricks to use when these "monsters" come up.
- Death from Above- Insects and arachnids are known for climbing up walls. Rats have also been seen crawling along pipes and beams up near the ceiling. If one of these things wanted to attack, the best way to do so would be to drop down on an unsuspecting party. The surprise mechanic is a GMs friend.
- Getting into Tight Spaces- So that fist-sized spider dropped down and scored a hit on your plate mail-clad fighter. How would the player react when, on the next round, it crawled underneath the breastplate and down the character's chest. Think about how people react when a normal bug is crawling on them, and take it up to 11.
- Remember the Filth Factor- Disease doesn't get played up in RPGs very much. Possibly because there isn't as much drama in combating the plague as there is trying to find the antidote to a rare poison. But it should be a possibility nonetheless. You don't even have to use it on the PCs right away. For example, their torchbearer could get bitten by a rat and succumb to a disease. The PCs then get to see the effects of the disease first hand without being taken out of the game right away. Then, on the next rat encounter, they may take the fight a bit more seriously.