Balgus is one of the three master swordsman
on all of Gaia. He lives in Fanelia and serves as one of the four samurai
there. He apparently has been training Van for some time, presumably ever
since Folken went off and didn't return. He berates the young king for
his swordfighting weaknesses, though he clearly plays a larger role in
Van's life. In a way, he is a father figure for the boy, as his real one
died when he was very young.
Balgus is alarmingly skilled
with weaponry (hence how he got the title of being a master swordsman).
Though he trains Van with a normal sword, it doesn't appear to be what
he uses for real battles. During the second episode, when Zaibach attacks,
Balgus doesn't bother to climb into a guymelef like the other samurai.
He just unveils a humungous sword (if you've ever seen Rurouni Kenshin,
think Zanba's sword, except more... sword-like) and 
goes
nuts, chopping off guymelef parts here and there.
Unfortunately, his glory
did not last. While trying to defend the country, Balgus received a direct
"laser" hit and fell to the ground, covered in blood (of course, this was
not shown in the cut version), right in front of the horrified Van and
Hitomi. The terror of the situation caused Hitomi to panic, and that provoked
the reaction of the pendant, therefore causing the reaction of the Escaflowne's
energist, therefore causing the familiar pillar of light to appear and
therefore transported Van and Hitomi to the outskirts of Asturia, thus
most likely saving them from immenent destruction.
Balgus actually played
a larger part in the series than most people are able to recognize. He
appeared only briefly in the first episode and then in the second episode.
However, in reality, he stayed within Van's heart. Van clearly loved and
respected Balgus, as a teacher but also as a second father. He feels compelled
to fufill Balgus's request, which was to protect Hitomi. Doing as Balgus
asked is probably what began to trigger his feelings for Hitomi.
Balgus appears once more
in episode... 14 and 15 (cut, in the uncut I think it would be 16 or 17,
I'm not sure), Balgus appears in Van's "Atlantis reality" to instruct Van
that he must fight.
He is 70 years old.