meed > reward

4 Of him that slew Sansfoy with bloody knife;

knife > sword

5 Henceforth his ghost, freed from repining strife,

ghost > spirit, soul repining > fretting, fretful

6 In peace may pass over Lethe Lake,

Lethe > (A river in hell; those who drink from it lose all memory of their former life and become purified; see SC, gloss to "March", Aen. 6.745-51, PL 2.604)

7 When mourning altars, purged with enemy's life,

purged > purified

8 The black infernal Furies do aslake: