The Bonus Merchants refers to special merchants that were added in the Collector's Version of the game, and perhaps the pre-ordered versions as well (not sure on that one).
There are two of them, one named Deidre, who will be in the Adventurer's Mart and another by the name of Joluv, who can be found in the Copper Coronet. If you've never seen either of these merchants before, you probably don't have the patch installed. [img]smile.gif[/img]
The Bonus Merchant patch can be found at
Sorcerer's Place. Just follow the instructions given to install. Note that if you have TOB installed, the latest TOB patch adds one of these merchants (but not both).
As far as Haer'Dalis goes, as F. Gottwald says, he can be extremely effective, considering the various mage spells that are available to him. I'd advise studying your spellbook and selecting some of the more combat-orientated spells for him to use such as Protection from Magical/Normal Weapons, Stoneskin(as mentioned) etc.
Haer'Dalis can specialize in short swords and long swords, but can only become proficient with other types of weapons. Outfit him with some strength modifying items (there are certainly plenty to choose from), use offensive spin, and enjoy the show. And, if you use Defensive Spin (in addition to the protection spells listed above), he can act as a decent tank as well.
He also has a decent lore rating - as well as a surprisingly high pickpockets ability (considering the fact that as a Blade, he *should* have only half of the regular bard ability).
Whether or not you choose to use him in your party is entirely up to you. [img]smile.gif[/img] But Haer'Dalis can be (and is one of my favorite characters, from a role-playing point of view) a good addition to your party, particularly if you already have a designated "tank" and are looking for some extra damage.