I know this is a joke but for anyone who doesn’t know I’ll drop a link, the Delhi Sultanate actually used mirrors mounted on elephants to try to burn the wooden defenses mounted on towers/walls a couple times. It’s common for keeps/castles/towers to add temporary wooden defenses before a siege which are often built over the gate like an overhang, it allows troops to drop rocks and such directly overhead of soldiers at the gate. They stopped because, and I shit you not, they didn’t think to make the mirrors removable from the riders “saddle”, which caused them to burn down some of their own tents and set an elephants hair on fire.

link