90's (or earlier) YA fantasy series with broken crystal said scattered across time, imbued with telepathic powers

Question

Not sure when the books were released, but I read them probably in the 93-95 era.

• There were multiple protagonists in this series and the viewpoints jumped around.
• I believe there was time travel involved and that some of the characters were from different times and the times got blurred at points.
• There was a crystal involved
• Each shard of this crystal was imbued with powers which were kind of telepathic in nature and characters, good and bad, were trying to gather multiple shards.
• I believe (this could be wrong) that mentally speaking with wolves and getting their help was one thing that the protagonists did.
• There was a series of caves being explored as well with shards being scattered across time

Answer 1

This is the "Children of Ynell" series by Shirley Rousseau Murphy.

The blurb for the fifth book ("The Joining of the Stone", 1981) describes the runestone as being in "shards" and there's also a mention of a wolf:

Lobon, son of Ramad of the Wolves, helped by the wolves and the Seers of Carriol, continues his father's struggle to find the shards of the runestone and unite them for the power of good. Sequel to "Caves of Fire and Ice."