The real Soulis died in prison and not as in the story, but the thing that happened to him may possibly have happened to someone else in roughly the same place. Legend and history agree that he was a bad man but not about him being a wizard.
Walter Scot's friend John Leyden wrote a ballad about Soulis at the beginning of the 19th century and Algernon Charles Swinburne had another go a century later. Neither version entirely pleases me. For one thing they're far too long. My version steals from both and from anyone else who happened to be passing because that's what ballad writers do.
I don't have a tune in mind, but there are bound to be dozens that would fit.
Lord Robert has gone hunting
Down by the water side
He loosed a shaft at a great grey heron;
The arrow turned aside
And out of the brake rode Lord Soulis,
His troopers at his knee.
How dare you hunt at Hermitage
And ask no leave of me.
Did you not ken there are eyes in the moss
That see you come and go?
Did you not ken they are bound to me
To tell me all they know?
Did you not ken I have servitors
That show to no man's sight?
It was one of them stood in your path
And turned your arrow's flight.
But I'll be fair to you, Robert,
Who were not fair to me.
I choose to hang you as a thief
But you can choose the tree.
I will not choose the good Scots pine
For since I was a child
Such have stood guard round my father's house
When winds blow high and wild.
I will not choose the hawthorn bright
For in the month of May
Its blossoms shade my mother's bower
And keep ill airs away.
But I will choose yon sturdy oak
For there my household stand,
Each with an arrow notched to the string
And his bow in his left hand.
All of them have good steel caps
And broadswords at their thighs
With sprigs of hazel in their coats
To blind your servants eyes.
They loosed the arrows from the string.
They shot the troopers dead.
The shafts they shot at Lord Soulis
Went whistling past his head.
They have bound Lord Soulis hand and foot
They have hauled him to the oak.
Three times they have hoisted him;
Three times the halter broke.
Lord Soulis laughed a mighty laugh
He said, you're much to blame.
Have you not heard of my master dear;
Michael Scot by name.
He gave me the word that turns a blade,
The word that stops a ball,
The word that keeps your bones unbroke
However far you fall.
There is no fire can singe my hair
No water can me drown.
Loose my bands and I'll speak you fair
To the king in Edinburgh town.
Then up there spoke an elder knight-
Michael Scot was my master too.
Fire may not burn him nor water drown
But what if we marry the two?
Carry him up to the Nine Stane Rig,
Hang a pot from the stones,
Light a great fire under it
And cook the meat from his bones.
The first hour he danced in the pot,
The next he cursed and swore,
The third hour his head sank down
And his voice was heard no more.
Then up there spake the elder knight.
He had been in foreign lands
And fought the paynim foot to foot
For cities in the sand.
I have seen men die for want of meat
And faint at the water stoup
But I never saw a man so weary
He drank his own self for soup.
The Nine Stane Rig is a dreary place
No birds sing thereabout
And no grass grows on the hill top where
They poured Lord Soulis out.