certainly > reliably, with certainty aread > make known

9 That I may wreak on them their heinous hateful deed."

That > [So that] wreak > visit [visit on them the equivalent of their misdeed]

203.15

Certes, my Lord, (said he) that shall I soone,
2 And giue you eke good helpe to their decay,
But mote I wisely you aduise to doon;
4 Giue no ods to your foes, but do puruay
Your selfe of sword before that bloudy day:
6 For they be two the prowest knights on ground,
And oft approu'd in many hard assay,
8 And eke of surest steele, that may be found,
Do arme your selfe against that day, them to confound.

1 "Certes, my lord," said he, "that shall I soon,

Certes > Assuredly that > [aread where those knights do lurk]

2 And give you eke good help to their decay,

eke > moreover to > [in bringing about] decay > destruction, death

3 But might I wisely you advise to do: