Automatic Coding said:
http://runescape.wikia.com/wiki/Spectral_spirit_shield
"The Spectral spirit shield was released on 15 September 2008 along with Summer's end. It requires 75 Defence, 70 Prayer and 65 Magic to wield. The shield is made by attaching a Spectral sigil to a Blessed spirit shield. To do this, players need 90 Prayer and 85 Smithing. Additionally, Brother Bordiss can be asked to attach it for 1,500,000 coins after completing Perils of Ice Mountain. To receive any sigil, Summer's End must be completed.
This shield is equivalent to an Arcane spirit shield, but instead of an offensive bonus of +20, it has a Magic defence bonus of +30. This shield is commonly used by wealthy players during Castle Wars and Tzhaar Fight Pits because of its extremely high magic defence. This shield is also effective in the Armadyl boss chamber as it gives good protection against Kree'arra's magic attacks, and is widely used among rangers when fighting the Corporeal Beast. It's equally the best shield for tanking the Zamorak boss who can hit you only with magic once pray melee is on. Its high magic defence bonuses also make it a good choice of shield to use on Slayer tasks, as commonly assigned monsters, such as Aberrant Spectres, Bloodvelds, Aquanites, and Waterfiends use magic-based attacks.
Both the Grand Exchange and "street" prices of the Spectral spirit shield have been known to fluctuate. At the time of its release, the price of the Spectral spirit shield stabilised in around the 40-50M range and was known to be the least expensive of the 'enhanced' spirit shields. Due to the Corporeal Beast's stomp attack update on 15 October 2008, its price steadily rose to more than 150 million coins, after which it started to drop again."
From RuneScape Wikia if you don't want to follow the link.
ON-TOPIC:
You made the right decision. They ARE crashing, if you ever want to buy one, wait about a week or two.