“All we want is the girl. Kill the rest.”
Zoldam is a member of the Black Fang and appears in Fire Emblem: The Blazing Blade, in the chapter Pirate Ship. His class is Shaman and he attacks Eliwood's (or Hector's) party as they are on board the Davros, Fargus's pirate ship, in pursuit of the escaping Ninian. He is noted to be quite difficult for that stage of the game, mainly due to his Luna tome. Fortunately, the chapter he appears in only requires the player to survive the chapter (he does not make a move to attack the party himself).
If the player does decide to attack him, most likely this is because he carries a valuable item, Speedwing, which, if wanted, must be stolen. If Zoldam is defeated, the chapter immediately ends, regardless of how many turns are left in the chapter, or if there are still player units left to move.
His sprite is a recolor of the sprite used for Heintz, the boss of Chapter 7 in Lyn's story.
Dark - B
* Normal Modes only
** Eliwood Hard Mode only
Zoldam's Luna tome is certainly a major threat. Units with anything less than 37 HP (46 in Hector's Hard Mode) stand a risk of getting killed in a single hit. Players wishing to obtain his item without risking an instant kill can use Matthew to steal his item and a Cavalier to rescue him from harm's reach.
Thankfully, Zoldam has mediocre speed,defense, and health. Thus, it should be possible to defeat him without giving him a chance to use Luna more than once. Using Supports that lower enemy critical chances (such as the support between Hector and Eliwood) can make the risk more manageable.