I have always taken the Wyrdstone Necklace on my Tyrant. Recently I have been looking into the comparison between the Spangleshard Talisman and the Wyrdstone Necklace.
The Wyrdstone Necklace grants a 5+ Ward Save with the minor negative that the Tyrant could take a wound after deployment.
The Spangleshard Talisman is a strange on. If wounded by strength 7 or better then you get a 3+ save. A strength 6 attack and its a 4+ save, Strength 5 is a 5+ save. Therefore attacks greater than Strength 5 the Spangleshard Talisman is better than the Wyrdstone Necklace.
Here is the snag against strength 4 the save is 6+ and strength 3 no save at all. This leaves the Tyrant at risk against normal infantry, magic missiles and Elven shooting when taking the Spangleshard Talisman over the Wyrdstone Necklace. Also the Spangleshard Talisman cannot be used against automatic wound items, but I don't see these very often.
I am now considered the Spangleshard Talisman on a Hunter, but at 30 points it restricts the magic weapons available to only the Sword of Might.
One option I quite like the look of is the Spangleshard Talisman and the Beastkiller big name on a Hunter. This combination could be used against dragons typically giving a 4+ save, also causing multiply wounds. I think I will probably run this combination for the Summer Incursion in a couple of weeks.