Vowing to win release,
The great seer, born in a line of royal seers,
Sat there, and the world rejoiced.
Shaking with fright, however, was the enemy of true dharma -- Mara.
The opening verse of the 13th canto, "Victory over Mara," of Buddha-carita is translated by Patrick Olivelle like this:
When that great seer, who was born in a line
of royal seers, sat down there with the pledge
to win release, the world rejoiced, and yet
Mara, foe of true Dharma, shook with fright.
I don't see anything to criticize in Patrick Olivelle's translation.
But when I examine the original four-line verse, through (I cannot deny it) the eyes of my teacher Gudo:
the first line is about the Buddha's mind;
the second line expresses objectively, in terms of his royal ancestry, who the Buddha was;
the third line centres on the actions of sitting and rejoicing; and
the fourth line describes, with poetic license, the real effect on the evil one -- poor old Mara.