Well he charms you in Red Box and that spell is on everyone's spell list so that doesn't narrow it down. He kills the cleric with a magic missile which is wizard and sorcerer only.
From "Red Arrow, Black Shield" he is listed as below as a level 15 Magic User. I always have pictured him as a Wizard myself with the robes.
"In addition, the Baron is accompanied by his personal Court Sorcerer, Bargle the Infamous (familiar to all who completed the first adventure in the D&D Basic Set).
Bargle the Infamous: AC 0; M 15; hp 30; MV 120' (40'); #AT1 dagger +2, +3 vs. spell-casters; D 1-4 +2 or +3; Save M15; ML 12; AL C; S 9; I 18; W 9; D 17; Co 12; Ch 15; XP 3,200
Level 1: charm person, magic missile (x2), shield, sleep
Level 2: detect invisible, invisibility, levitate, phantasmal force
Level 3: dispel magic, fire ball (x2), protection from normal missiles
Level 4: hallucinatory terrain, ice storm/wall, massmorph, wall of fire
Level 5: cloudkill, conjure elemental, wall of stone
Level 6: anti-magic shell, disintegrate
Level 7: power word stun
Bracers of defense AC 2, dagger +2 (+3 vs. spell-casters), scroll of protection from magic, ring of regeneration, drums of panic"
As for escape, Cape of the Montebank is always useful.