Helliweg

Helliweg is a character in the fifth season, appearing in "The Wars to Come". He is a young member of the Order of Maesters, and is in service to House Royce at Runestone.

Season 5
Helliweg is attending the Melee at Runestone when a raven arrives for Lord Petyr Baelish. The young maester delivers the message to it's recipient before departing

In the books
In the A Song of Ice and Fire novels, Helliweg is also the maester of Runestone. However, unlike his TV counterpart he is described as being particularly aged and venerable.