Was Glorfindel's horse one of the Mearas?

[Inziladun]

Originally Posted by Gorthaur the Cruel

It may be that the reason Shadowfax was able to endure the Witch-king was because his rider was none other than the bearer of Narya, the ring of fire that kindled hearts, rather than his own breed.

It's an intriguing idea. I'm inclined to think the courage of Shadowfax was due to his mearas status, with perhaps Gandalf being the White providing an enhancement. No doubt Narya would have been a help as well.

Originally Posted by Gorthaur the Cruel

In the case, of Bill the pony, he was also under rejuvenating effects of Vilya, the ring of air, used to preserve and maintain Rivendell. Why else was Bilbo ale to age still so slowly even bereft of the One? It's because he also dwelt under the influence of Vilya in Rivendell, for a time.

I have to disagree here. I think the 'mark' left by the Ring was what sustained Bilbo. It certainly did the trick for Gollum, even though he too was bereft of physical possession of the One.