This merchant on the streets of the Inner City has no name (Identified only as "Talk to Merchant"). He sells Herbs, which have some restorative properties when consumed and can also be used to create potions using the Alchemy skill.
Like most of the outdoor Traders in Venice, he can only be found at his sales cart during daylight hours.
He sells herbs at his vendor stand ouside the Garrison:
Like other merchants, he can also buy unneeded items Scarlett wishes to sell, converting them to ducats she can spend on more useful items. (He will also be able to sell back to Scarlett any items she previously sold to him, though at a substantial markup price.)
Interestingly, this merchant, although he obviously specializes in White Ivy and Dusk Whin, does not pay any higher rate for those herbs, unlike Master Deimos, who pays twice the going rate.
This merchant can be found can be found just outside Garrison during most daylight hours.