There's another legendary stone at the church (it seems one is not enough)? It's the lintel above the Priest's Door.
Owen usually attended divine service at Corwen Church, where I was shown a doorway now made up through which he entered to his pew in the chancel. Upon one of the stones is cut, half an inch deep, the figure of a dagger, and my guide told me, with a face more serious than my own, "that upon the Berwyn mountain, behind the Church, was a place called Glyndwr's seat, from which he threw his dagger, and made the impression upon the stone." If this had happened in our day, the whole bench of bishops would have united in pronouncing him Jacobin. Exclusive of the improbability of the tale, my friend forgot that it refutes itself, for the mark of the dagger is upon the very door-way which Owen passed, which probably was not built up in his day. I climbed the mountain to what is called Owain's seat, among the rocks, and concluded he must have been more agreeably employed than in throwing his dagger, for the prospect is most charming. Here the rich and delightful vale of Corwen expands to view, with the Dee in the centre. Here Owen might view near forty square miles of his own land.
In Thomas's History of the Diocese of St. Asaph, p. 687, the legend connected with the erection of the present church is given as follows: --
"The legend of its (Corwen Church) original foundation states that all attempts to build the church in any other spot than where stood the 'Carreg y Big yn y fach rewlyd,' i.e., 'The pointed stone in the icy nook,' were frustrated by the influence of certain adverse powers."
No agency is mentioned in this narrative. When questioned on such a matter, the aged, of forty years ago, would shake their heads in an ominous kind of manner, and remain silent, as if it were wrong on their part to allude to the affair. Others, more bold, would surmise that it was the work of a Spirit, or of the Fairies.
From p175 of 'Welsh Folk Lore' by the Rev. Elias Owen (1887) - online at Project Gutenberg.
Evidently the Rev was taking some of his words from Thomas Pennant:
A Monument of our superstition remains in the Carreg y Big yn y fach Rewlyd, a pointed rude stone, which stands near the porch. We are told that all attempts to build the church in any other place, were frustrated by the influence of certain adverse powers, till the founders, warned in vision, were directed ot the spot where this pillar stood.