Descendo likely causes any targeted object to move downwards.
History
In 1997, it is used by Ron Weasley to magically cause the stairs in his room, which lead to the attic, to descend, as well as by Vincent Crabbe in the Room of Requirement to lower the wall behind which Ron is hiding.
Etymology
Descendo is Latin for "I descend".
Pronunciation
deh-SEN-doh (IPA: /dɛ.ˈsɛn.dəʊ/)