Harold

Harold, awakened, the Left hand of Messire and Commander over the male Vanguards. He was first briefly mentioned by Nina as the one who is hunting Blanc for the Vanguards and got labeled as one of the strongest Vanguards by her. (c17) He again is mentioned by Vega as the one who should deal with Cassandra. (c58) Again Harold got announced as the one to hunt down Alice by Icolde. (c46)

From this pattern it seems Harold's job is to get rid from opposition of Abyssal level for the Vanguards. There is a very good chance that Harold is 23.