This is probably me clinging onto THE GUARDIAN HERD series but, doesn't it feel weird that it's called RIDERS OF THE REALM?
When the second arc was first being developed, it was under the name of THE GUARDIAN HERD: DARK WATER TRIALS.
To me personally, since my exposure to the WARRIORS series by Erin Hunter, I honestly wished they kept the title of THE GUARDIAN HERD: DARK WATER TRIALS for the second arc.
I feel that by giving this arc a different name it makes the first arc unneccessarily difficult to locate on libraries to new readers.
i have to be honest i had the riders of the realm then thought the guardian herd: across the dark waters was a separate book. XD