Demonic Seals are in many ways an ineffective weapon, but they are an amazing tool. They must be applied directly to the Demon's body, and the Demon's own energy immediately goes to work at breaking down the seal. However for the duration they are active they work by "freezing" the Demon's own energies, effectively locking the demon in place.

Because of this it can scale to, theoretically, any level. However although any Demon CAN be locked down, the more powerful they are the faster they will be able to break out.

To get around this you can try applying many seals and rotating them as they degrade. This can be very expensive, but it is one of the few effective ways of transporting a Demon any distance.

Technically Demonic Seals can be applied to Humans and Monsters, but because they are not as energy dense it only causes numbness and tingling at the point of contact. 

(In a pinch it can be used to relieve a headache.)

-Excerpt from a Sacred Text for use ONLY by Priests, on the method of containing Demons for study