This is my own interpretation of the ROD backed up up by Trell and Amok.
Earthpower exists by itself.
Lore allows for it's manipulation to do certain acts.
The lore or skill to manipulate Earthpower was at it's highest during Kevin's reign.
Let's think about the power levels the Old Lords used to wield.
Trothguard was devastated in the wars before the Ritual.
So much so that it refused growth even when the rest of the Land had recovered from Kevin's ROD.
How the heck did those Old Lords achieve such ruin?
By Lords using Earthpower guided by the passion of their lore.
Those Old Lords must have blasted the living hell out of the land in that area.
The only thing that we know of in the Land can can do that is the ROD.
The only restriction the Old Lords had at that time was the limits of their lore and the normal self preservation of being human.
They were each capable of their own ROD.
I like to think of them like tactical RODs.
But they had no despair at that time, they didn't want to kill themselves so their "RODs" were limited to the task at hand.
Also, to them there was no term "ROD", it was just the expression of their utmost power.
Amok said anyone could preform the ROD.
Could Triock?
Yes but of a limited scope based on his lore.
He could desecrate himself, his soul perhaps but that's it due to his limited lore.
Trell started the "ROD" and he was only the master of the rhadhamaerl.
I always got the impression that Trell's ROD would have been limited in scope to destroying Revelstone that he loved. That was the limit of his power and his goal.
So how did Trell learn the "Ritual"?
He didn't!
Because "Ritual" is misleading.
It leads us to believe it's a set of rules needed to be performed to achieve the end.
When in fact it's all about the individual's passions mixed with the individual's power lore.
Mhoram realizes that the Oath of Peace has put a cap on the New Lord's passions.
It's passion that invokes Earthpower.
Lore just focuses the passion.
What makes Kevin so important in regards to the ROD is that he was both the master of Earthpower and he held the Staff of Law but for the first time he was overcome with despair.
It's possible that he was the first of the Old Lords to lose hope in that way.
The challenge to Lord Foul by Kevin was a contest of wills not some elaborate ritual performed by the two of them.
Kevin believed that using the utmost of his power, the extreme limit of Kevin's very existence he could eradicate Foul, wipe him from the Earth.
It was at the end before he died and Foul was laughing at him that he realized his error.
It was the suicidal element, the despair element that triggered the runaway uncontrollable devastation that destroyed the Land.
The Old Lords didn't have this element.
Kevin did though and he also had the passion and power.
Kevin was the "perfect storm".
So even if there was no Oath none of the New Lords (at their level of lore) could have wiped out the Land like Kevin did because they lacked the lore or the power level to do so.
If Mhoram, now knowing how to invoke the ROD, wanted to sacrifice himself in a blaze or Earthpower and despair like Kevin it would have been in far limited scope.
Recovery of the other Wards would have given them more lore and thus the potential to match Kevin's destruction.
But only if they also had the equal passion and despair as well.
Now I await Wayfriend and others to turn all my ideas on it's head!
And I mean that in the best possible way!
