2 Through countries waste, and eke well edified,

waste > desolate, uncultivated eke > also [through countries] edified > built up, built over

3 Seeking adventures hard, to exercise 4 Their puissance, whilom full dernly tried:

puissance > power, strength whilom > formerly; recently full dernly tried > very severely put to the test (this use of "dernly" is SUS)

5 At length they came into a forest wide, 6 Whose hideous horror and sad trembling sound 7 Full grisly seemed: therein they long did ride,

Full > Very, exceedingly grisly > horrible, fearsome

8 Yet tract of living creatures none they found,

tract > track, trace

9 Save bears, lions, and bulls, which roamed them around.

301.15