1 But if you, Sir Satyrane, did weet

weet > know; discover

2 (Or you, Sir Peridure) her sorry state,

Peridure > (The spelling indicates a meaning like "Endurance" or "He
Who Persists". Possibly the intended hero of an unknown book of
FQ)
sorry > painful, distressing

3 How soon would you assemble many a fleet, 4 To fetch from sea that you at land lost late;

that > [she whom] late > lately

5 Towers, cities, kingdoms, you would ruinate

ruinate > demolish; lay waste; overthrow

6 In your avengement and dispiteous rage,

avengement > vengeance dispiteous > pitiless