Dragonfire shield

Dragonfire shield is one of the best shields in game. It requires 75 defence to wear. Dragonfire shield offer two special defences: Acts like regular Anti-Dragon Shield in terms of dragonfire protection. But it also protects from Skeletal Wyverns similarly to Mirror Shield.

Bonuses
Dragonfire shield has is unique in terms of defence it gives. When its "uncharged", it is tradeable and offers slightly more defences than Mithril Sq Shield. However, when fully charged it is one of the best shields in the game, if not the best.

To charge Dfs, you will need to absorb dragonfire attacks while wearing it. Every absorbion increases effective defences by +1, to peak of +50 defence increase.

Metal Dragons are best way to do it, since if you keep your distance they will only use breath attack.(Protect from magic or antifire potion conjunction is recommended to prevent any damage taken)

Obtaining Dragonfire shield
Dragonfire shield is not dropped by any NPCs. To obtain one, you will need Dragonic Visage and Anti-Dragon shield. Then you have to attach them together with hammer at anvil. This requires 90 smithing and smithing them together grants 2000 smithing xp.

Alternatively, you can take Visage and Anti-Dragon shield to Oziach at Edgeville, and pay him 1,250,000 coins to smith them together.

Special ability

By right clicking Dragonfire shield you can select "discharge". This will take one charge off. Also, when you attack someone it will launch dragonfire attack on them. One charge can deal high as 25 damage. But, if enemy is wearing Anti-Dragon Shield, Dfs, or under effect of Protect from Magic/antifire potion, then effectiviness of attack is greatly reduced. You can only do this once in 10 minutes.

If you want get rid of charges fast you can just select "release" on right click options which will release all charges in harmless burst.

Trivia
 * Dragonfire shields are very useful for Defence pures, not only because of the massive defences  they give but because of dragonfire attack.