Here are the side effects of the Bounty Hunter special traps.
1st: The trap deals out damage and slows the target
11th: The trap holds the target
16th: The trap erects an Otiluke's Resilient Sphere around the target
21st: The trap Mazes the target.
I have never seen anything that lists the actual damage for these or the basic traps. My own experience is that the damage tends to be between 20 and 40 points.
EDIT: I spoke too soon. Here is some info from the
Thief Guide at GameFaqs. I have no idea how accurate it is:
NORMAL TRAPS
Level 1 Trap: Doesn't exist, since you start off higher than level 6.
Level 6 Trap: Deals 2d8+5 damage to any enemies within the area
of effect of the Trap when it goes off. This is non-magical damage
so Magic Resistence can't stop it (as is the same for all initial
damage of later Traps).
Level 11 Trap: Deals 2d8+5 damage to any enemies within the area
of effect of the Trap when it goes off. In addition, for the next
three rounds, it deals 2d6 poison damage per round (hence
resistence or vulnerability to poison also affects the damage).
In addition, this extra damage also disrupts spell casting (like
Melf's Acid Arrow).
Level 16 Trap: Deals 3d8+5 damage plus 4d8+2 fire damage to any
enemies within the area of effect of the Trap when it goes off.
Like poison, any vulnerability or resistence to fire also effects
the extra damage.
Level 21 Trap: Deals 3d8+5 damage plus 20 poison damage to any
enemies within the area of effect of the Trap when it goes off.
Plus, enemies must Save vs Death with a +4 bonus or die instantly.
Again, the poison damage can be reduced or increased according to
resistence/vulnerability.
SPECIAL TRAPS
Level 1 Special Trap: Doesn't exist, since you start off higher than
level 6.
Level 6 Special Trap: Deals 3d8+5 damage to any enemies within the
area of effect of the Special Trap when it goes off. In addition,
enemies must Save vs. Spells with a -4 penalty or be slowed for 5
rounds. (Like normal Traps, the initial damage is non-magical.)
Level 11 Special Trap: Deals 4d8+5 damage to any enemies within the
area of effect of the Special Trap when it goes off. In addition,
humanoid enemies must Save vs. Spells with a -1 penalty or be
held for 5 rounds.
Level 16 Special Trap: All enemies within the area of effect when
the Special Trap goes off must Save vs. Spells or be affected as
Otiluke's Resilient Sphere for 7 rounds.
Level 21 Special Trap: All enemies within the area of effect,
regardless of Magic Resistence, are Mazed as the spell of the same
name (except Spell Trap and the like cannot stop it from occuring).
The Maze lasts according to intelligence, as according to the
actual spell.
