"How to gain a throne in ancient Ireland"
or
"Who left the back gate open?"
ochy greets his young son with open arms and of course they start talking about the boy's future. Aengus has to have a kingdom. Eochy tells him that his inheritance, through his mother, is still being lorded over by Elcmar. Aengus is impatient to get on with kinging it, so he throws a cute little temper tantrum and cracks the ceiling with a scream. Eochy gives him a fatherly cuff behind the ear and tells him to settle down. He informs Aengus that Elcmar is such a tool that it should be easy to trick him out of his throne. He whispers a plan into Aengus' ear. Psssst sssss sssst pssst.... Aengus' dear little pout slowly breaks into a broad smile. He wipes away his darling little tears and nods vigorously, a mischievous glint in his eye.Aengus borrows a chariot and goes to visit Elcmar (these princes must travel in style y'know..). He picks his moment well. Elcmar is watching a hurley game (field hockey) and is unarmed and unprepared. Aengus sneaks up behind him, pulls out a knife, rams a couple of fingers up Elcmar's nostrils, yanks his head back and holds the blade to Elcmar's throat. Elcmar can't do a thing; he just about pees his britches.
"Flease don't kill me!" he begs.
"I won't, if you let me sit on your throne and rule in your place for a day and a night", promises Aengus.
Elcmar doesn't like this, but Hobson's Choice; he's got no option, see. And he figures, what the hell... it's only 24 hours. Then he can deal with this impudent little bastard afterwards. He agrees to Aengus' terms. Aengus releases him and they shake on it.
The boy sits on the throne and does a great job as ruler of Elcmar's land for a day and a night. After all, he is a natural born ruler, with some of his Dad's magical skills. But when Elcmar comes to reclaim his throne, Aengus won't give it up.

Elcmar cries "Foul!" and curses at the boy, calling him a dishonourable nasty person who goes back on his agreements. Aengus takes that cutting insult on the chin and smiles and suggests they bring in King Eochy as an arbitrator for this dispute. Everybody else just stands around like a bunch of stunned gobshites. It doesn't pay to mess in the affairs of the nobility they've learned long and long ago.
Elcmar says, "Sure thing, me boyo! Eochy's my bud from way back and I'm way in the right here." He wiggles a finger in Aengus' face, "You're gonna be left twisting in the wind, Buck. You'll see."
Aengus just smiles nicely at Elcmar. They send a request to Eochy to come as soon as he can.
Well, Eochy gets there almost immediately and listens to the whole story without an interruption, hearing both sides out. When he's heard it all, he sits back, takes a drag on his cigarette, butts it out while blowing the smoke out the side of his mouth, scratches his chin absently, shoots a furtive wink at Eithne who smiles to herself, and draws a deep breath.
He puts on an impassive lordly face and says in Charlton Heston-like tones: "Elcmar, my judgement goeth against thee. Thou hath granted to Aengus that he may sit thy throne for day and night which leaveth no time for thyself to rule. Also, thou hast shown that thou regardest thy life above thy responsibilities as ruler and giveth over thy throne overly... overly... um... overly quickethly. Hence thou art not fit to rule over others. So be it written that thy throne hath pathetheth to Aengus... That should just about do it. Hey, let's all get pissed and play Naked Twister!"
With that, there was a great cheer (Eochy knows what the people like) and Elcmar slinks away from the party, with his tail between his legs, thinking, "Well Jeez, that really blows... I got royally screwed there! "
And that's how Aengus snagged his throne.
Okay, actually Eochy was a pretty good shit when it suited him, so he gives Elcmar some land to rule over which was of equal value to what he'd lost, though it was pretty far away. That kept him out of the picture for good and meant he didn't need to worry about a lifelong enemy in the guy, even if he wasn't much of a threat. And Elcmar was happy enough to be further away from these folk, so he made no more trouble; just took the money and ran. I know you were probably feeling sorry for the poor sap, but things didn't work out too badly for him in the end. And he got some lovely parting gifts ( a washer/dryer and a dinette set) from both the father and the son and a pat on the back and a "Thanks for playing our game... Johnny, let's meet our next contestant..."
Elcmar just takes his wife and leaves. Eithne and Eochy had had their fling and it was over, so she says, "Vaya con Dios!" and goes with her dim but loyal hubbie. `Twas lust, not love, after all. So they're out of the story, now.
Ah, but Eochy gets his comeuppance by the end, as you'll see...