relics > (Of her army)

2 Fought with Severus, and him overthrew;

Severus > (Lucius Septimus Severus, 146-211; Roman emperor 193-211.
Spent the last three years of his life in Britain, and died at
Eboracum (York))

3 Yet in the chase was slain of them that fled:

of > by

4 So made them victors, whom he did subdue. 5 Then gan Carausius tyrannize anew,

gan > did; began to Carausius > (Marcus Aurelius Valerius Carausius, c. 250-293. He seized control of Britain and proclaimed himself emperor, between 290-2 even receiving a modicum of acceptance from Rome) tyrannize > tyrannize; rule

6 And gainst the Romans bent their proper power,

gainst > against bent > turned, directed proper > own

7 But him Allectus treacherously slew,