oppressed > took by surprise; overwhelmed

9 The heavy plague that for such lechers is prepared.

heavy > grievous plague > blow, stroke (see 305.23; also, noted by Hamilton (1980), possibly a reference to venereal disease)

305.15

For soone as he was vanisht out of sight,
2 His coward courage gan emboldned bee,
And cast t'auenge him of that fowle despight,
4 Which he had borne of his bold enimee.
Tho to his brethren came: for they were three
6 Vngratious children of one gracelesse sire,
And vnto them complained, how that he
8 Had vsed bene of that foolehardy Squire;
So them with bitter words he stird to bloudy ire.

1 For, soon as he was vanished out of sight,

soon > [as soon]

2 His coward courage began emboldened be,

courage > heart, spirit be > [to be]

3 And cast to avenge him of that foul despite