Historically, most tombs known to have grave goods in them were robbed soon after the dead person was laid to rest. So why has the tomb that your group of adventurers broken into not already suffered this fate?
Sneezing Sickness - A strange plant infection that causes its victim to spread the plants seeds by sneezing them about. Larger lumps of phlegm or saliva sprout is spat out in a sunny place, producing more of the plants. As the Magical version of seasonaly allergies the affliction is limited in term and non-life threatening.