1 By strange occasion she did him behold,
occasion > circumstances
2 And much more strangely began to love his sight,
sight > appearance
3 As it in books has written been of old. 4 In Dehenbarth (that now South Wales is hight,
Dehenbarth > (The name given by Holinshed, Chronicles 1.26, for South Wales) hight > called
5 What time King Ryence reigned, and dealed right)
What time > [At the time when] Ryence > (Named in Malory 38-41) dealed > acted, proceeded [in respect of his subjects]
6 The great magician Merlin had devised, 7 By his deep science, and hell-dreaded might,
science > learning, knowledge, skill; hence: magic, occult powers