It appears that the speaker views winter as a powerful and formidable foe that is difficult to vanquish. If you examine the first stanza, the speaker notes that winter is 'deep-founded'. In the second stanza, winter is described as a man (perhaps a king?) who 'rear’d his sceptre o’er the world'. In classic fantasy, sceptres are often wielded with power and sometimes magic that is used to destroy.
