If Azzanadra's Seal is lost, you'll "find it on the ground and then pick it up" automatically, which means if you die with full barrows, or something else like that, with prayers for protection of items, you'll keep those items and the seal.
If you invoke the seals they will give you a specific effect. Imp Invoking grants you a Rusty Imp Dagger. This gives you -10 strength and no other stats. If your attack is against any pickpocketable enemy, the damage you do will be determined by the number of times you steal from them without getting arrested. If you attempt to attack an opponent whose ability to steal is too low, you will only fight the enemy.
The hidden +5 bonus to theft is given by this dagger. If you take on a guard equipped with the dagger and 35 thieving you will be able take their money. The seal is destroyed after you have the item after killing Zamorak and Zamorak, however, if have Azzanadra's Seal, you can purchase a replacement seal from an imp, if you have lost your dagger.
Lesser Demon invoked will provide sword shards in black. Greater Demon invoking will grant red sword chunks. K'ril Tsutsaroth ~ invoking will give you demonic blade plans as well as an hilt of the sword. The Demon Butler (it's item name is Alathazdrar's Seal however the info on the exam says it's the demon butler's) When invoked, it will take you to Sergeant Damien. When you invoke again, it grants you 200 curry bowls.