Gabranth's full-plated appearance is based off of the Judges that were featured on the limited edition poster that came with Final Fantasy Tactics Advance (the same artwork was used for the box art of the game's North American release). As Yoshida Akihiko's note next to Gabranth's concept art in the Final Fantasy XII Ultimania Omega stated:
An illustration of a Judge riding a Chocobo is drawn on the Final Fantasy Tactics Advance poster, and Gabranth is designed under that drawing. Once the polygon model based on that design is finished, it seemed that something was lacking around the shoulders, so after receiving various indications of such, a modification was made.5
Similar to most video game characters, Gabranth wears the same suit of armor for the entity of the game (if one does not count the incident that took place two years prior to the rest of the game). Unlike most video game characters, wearing the same suit of armor day in and day out actually makes logical sense in Gabranth’s case since his armor serves as his uniform as Judge Magister.
In his interview on the bonus DVD that came with the collector’s edition of Final Fantasy XII, Yoshida said that Gabranth’s armor design was born out of the concept of freedom and based off of mountain biking gears.6 Although every Judge Magister comes with a uniquely designed set of full-plate armor, the full-face helmet is the most distinguishable feature between the various Judge Magisters.
For Gabranth, the top half of his helmet consists of a cross shaped spike at the very top, a visor just above the eyes, and horns reminisce of a ram’s extending from both sides. According to Yoshida, the design for Gabranth’s helmet is based off of his own bike helmet.7
Surprisingly, Gabranth's helmet seems fairly breathable. The helmet contains two large eye holes, two wide, v-shaped holes around the nose area, and rectangular holes across the top of the visor. Along with the rest of his full-plate armor, the helmet is decorated with embossed designs in silver.
A 1:1 replica of Gabranth's helmet was released by Square-Enix in 2008 as part of the Artifacts Collection, of which only 500 were made and is the most expensive piece of FFXII merchandise sold at 114,000 yen (roughly 1000 USD).
It is revealed within the game that Gabranth and Basch are (identical) twins hence they share very similar physical appearance. In the Scenario Ultimania, Yoshida mentioned that although he thought it would be best if people will notice who’s who just by looking at the drawing, it was a struggle to make Gabranth resemble Basch.8
From the CG renderings, both Gabranth and Basch possess downturned deep set hooded hazel eyes that are narrower when compared to the rest of the main cast. Between Gabranth and Basch, it seems that Gabranth has slightly droopier eyes and slightly more arched eyebrows. Gabranth also tends to have a colder, more intense gaze, while Basch tends to have a warmer, slightly softer gaze.
The world of Ivalice is populated by different cultures and races, so it is entirely possible that hair color is a regional trait within this fictional world. Both Gabranth and Basch have honey blonde hair, a darker shade of blonde compared to those from the central region of the world map, such as Vaan, Penelo (Dalmasca) and Rassler (Nabradia).
Although both Gabranth and Basch have the same hair color, each prefers to wear his hair differently. Gabranth tends to wear his hair short, in a hairstyle similar to Bathier’s, while Basch prefers to have his hair a little longer than chin length and not intently styled. From Yoshida’s illustration shown during the ending credits, it appears that Gabranth and Basch have always preferred to have different hairstyles, even during their younger days. Similarly, Gabranth also prefer to shave his facial hair, whilst Basch likes to keep his facial hair.