TRAPS
Fire Blast: Max
Lightning Sentry: Max
Death Sentry: Max

If you truly want to build a trapper you'll also put points into
Shock Web: 0 or Max
or
Charged Bolt Sentry: 0 or Max
to synergize FB and LS.

SHADOW DISCIPLINES
Cloak of Shadows: 1p
Mindblast: 1p
Weapon Block: 1p
Shadow Master: 1p
Burst of Speed: 1p
Fade: 0 or 1p

I much prefer running a trapper with BoS than Fade. You'll know why when you
start laying traps with Fade on and the Blade of Ali Baba in your right
hand. Some people prefer a meatier shadow, but good use of Mindblast and
Cloak of Shadows saves you a lot of skill points in my book. Weapon Block is
good enough with a single point. With a trapper you can stay far away from
the monsters.

MARTIAL ARTS
Dragon Flight: 1p

Teleporting your merc and shadow to the monster of your choice. If you're
super lucky and find a claw with DF you'll save four skill points here.

STAT POINTS
Enough strength and dexterity for your gear and the rest in vitality. A
trapper is not as mana hungry as a sorceress.

EQUIPMENT
The good thing with a trapper is that her gear can be shopped for. If you
want to twink her give her claws with various amount of trap
skills/assassion skills. If prefer a setup with +3/+3 trap skills on primary
and +3/+3 shadow skills on switch.

The rest of her gear is pretty much similar to sorceress gear. Vipermagi,
Shako if you're rich/fortunate enough, Arachnid Mesh and so on. Basically
what you want is + to assassin skills or trap skills. I refuse to look at
the new ladder only rune words, but some of them could be useful to a
trapper. But I'm not looking!

MERCENARY
I've used a Defiance and a Holy Freeze merc but I would seriously consider a
Might merc. Why? To get that first body for your Death Sentry!

desktop at home dot se

Max Fire Bomb, Lightning Sentry, and put a lot of points in Death Sentry,
and the various synergies.

Also put enough points to get at least a lvl 17 Shadow Master. One point
in various one-point wonders like Mind Blast, Fade, Weapon Block, etc.

Equipment-wise: + skills stuff. Shop Anya in NM for a pair of +3 traps
and a pair of +3 shadow claws. Skin of Viper Magi for res-all and
resists, but other armours work too. Shako would be nice. Frostburns for
extra mana worked fine for mine.

A trapper is not that equipment-dependent, really.

Have fun, because it's a fun character to play...!

Patrick.

SC or HC, SP or realm?

Others have posted good advice on skill and stat distribution (note
that my ironman trapper had few mana problems at base Energy, even
though she couldn't buy the stuff).  I like to use SW rather than SM,
because it gives me more control: in 1.10, your Shadow's traps can
delete your traps, and she probably doesn't know the best places to
cast them.  LIs are the only real challenge for a trapper, and there
are ways to deal with them.  BF is a one-point wonder that can be
tremendously useful for getting that first kill for your DS.  One
point in Venom combined with BF pretty much stops monster regen when
necessary, except with poison-immunes.  CoS is another good
one-pointer, and you should use it liberally.

-- Roy L