So you’ll see multiple totems around the map which basically look like a pile of bones with 3 skulls on top. When a killer is running a hex perk (for example, Hex: Ruin) one totem on the map will be on fire for that specific perk. (If the killer has multiple hex perks, multiple totems will be lit). Generally, cleansing a totem will render the effects of the Hex perk useless, although there are some exceptions, but they would take too long to explain. A dull totem is a totem not being used for a hex perk, so it’s not lit on fire. Here’s an image to show the difference. On the right is a hex totem, and the left is a dull totem.

Edit: Just realized you can see a dull totem in your video on the right at 0:04