Mag Sléacht: The Plain of Adoration
Here used to be
A high idol with many fights,
Which was named the Cromm Cruaich;
It made every tribe to be without peace.
'T was a sad evil!
Brave Gaels used to worship it.
From it they would not without tribute ask
To be satisfied as to their portion of the hard world
He was their god the withered Cromm with many mists,
The people whom he shook over every host,
The everlasting kingdom they shall not have.
To him without glory
They would kill their piteous, wretched offspring
With much wailing and peril,
To pour their blood around Cromm Cruaich.
Milk and Corn
They would ask from him speedily,
In return for one third of their healthy issue,
Great was the horror and scare of him.
To him noble Gaels would prostrate themselves,
From the worship of him with many man-slaughters,
The plain is called "Mag Slecht".
They did evil,
They did beat their palms,
They pounded their bodies,
Wailing to the demon who enslaved them.
Around Cromm Cruaich,
The hosts would prostrate themselves,
Though he put them under deadly disgrace,
Their name clings to the noble plain.
In their ranks (stood),
Four times three stone idols,
To bitterly beguile the hosts,
The figure of the Cromm was made of gold.
Since the rule of Herimon,
The noble man of grace,
There was worshipping of stones,
Until the coming of the good Patrick of Macha.
A sledge hammer he applied to the Cromm,
He applied from crown to sole,
He destroyed without lack of valour,
The feeble idol which was there.
********
There came Tigernmas prince of Tara yonder,
On Halloween with many hosts,
A cause of grief to them was the deed.
Dead were the men of Banba's host without happy strength,
Around Tigernmas, the destructive man of the North,
From the worship of Cromm Cruaich,
It was no luck to them.
For I have learnt,
Except one fourth of the keen Gaels,
Not a man alive lasting the snare!
Escaped without death in his mouth."
NOTES
This is actually the only known reference to human sacrifice on Irish soil in Irish literature. Otherwise, the practice seems to have been unknown; indeed, this story may not even be native, but influenced by the story of the Biblical Moloch.
However, human sacrifice was known in Britain, as evidenced by the bogmen. If there are any Irish bogmen, I have not heard about them, but that doesn't rule out their existence.
SOURCE: Kuno Meyer's translation of the Dindshenchas of Mag Slecht. Found in Celtic Myths and Legends by Charles Squire, first published 1890.