This isn't a bad item, but is it really worth 25 more points than a Talisman of Preservation for a chance to do more wounds occasionally? I don't think so, personally.
Talisman of Preservation
For 5 points cheaper you can take the Pendant, which is usually better. However, this is always usable which is a nice feature at times. Certainly not a bad choice, especially if the Pendant is already being used.
Pretty good, and probably going to be pretty standard for at least one character to take. 3 Null Talismans is the same points with the same effect, so you could protect two units from magic using this.
Ring of Darkness
It's only going to be useful with the Glittering Scales if you're going for that sort of build. Other than that, it doesn't provide that much help against shooting, and will only help you in close combat slightly.
Pendant of Khaeleth
A fantastic item, made even better because it's a great defense against suffering miscasts. I would expect to see this in every list for one of the characters.
Talisman of Endurance
Inferior to the Pendant and really not a good value for the protection it offers.
I don't really see much point of this, honestly. If you're going to get the protection from MR, why not get MR(3)? If you don't have the points, then I suppose this suffices.
Seal of Ghrond
A good choice in 8th edition, given how dispel dice are generated. You're going to love having an extra dispel die from time to time, and you aren't really paying all that much for it. Will find its way in a few lists. Since Magic Resistance changed to a ward save, you're going to need to find other ways to power your dispelling ability.
Pearl of Infinite Bleakness
If you have a Sorceress with the Sacrificial Dagger, you'll want to include this. Keeping the unit from running for whatever reason will be a huge help, especially later in the game when your greedy sacrificing is causing panic checks.
Ring of Hotek
They've changed this item so that it only affects wizards casting their spells within a specific range (instead of targeting). Overall, I think this change is better for the game, although this really hurts the utility of the item. Unless you are running the build that people occasionally tried in 7th (Master on a Dark Pegasus, Ring of Hotek, and Cloak of Hag Graef with a crossbow and lance), I don't think you're going to see this make any more appearances.
Taking this with the Armor of Darkness provides some pretty great protection for cheap. Of course, if you lose your armor save, you're screwed, but even an armor piercing weapon will still provide you enough of a chance to use this. I could see taking it from time to time.
I don't think this is going to be worth it. One-time protection just isn't going to cut it when you're going to see a lot more attacks coming at you.
If you're only looking at MR(1), it's probably not going to be worth it... for a character. On a unit it's kind of cool, but generally you're better off taking a weapon for that unit if you can.
Just read what I wrote about the Obsidian Lodestone, Amulet, or Trinket to see what I think for this choice. Overall, you'll probably see it.
Talisman of Protection
A 6+ Ward for a character really isn't going to protect you much. Pass.
Seed of Rebirth
A 6+ Ward for a character that you can negate easily is going to help you even less.
A fantastic addition to your defensive load if you aren't already taking a Talisman. Partners very well with the Armour of Eternal Servitude.
Pidgeon Plucker Pendant
Oooooh, a very specialized 5+ ward save! Probably not much use in this edition. Utterly worthless against a lot of armies.
Even though it's 5 points, I don't see it ever getting used. You need better things if you want good protection.