I always wanted to build a dexxer around the Ninjitsu move 'focus attack'.
My idea was to run something like this:
120 ninja
120 swords
120 tactics
120 heal
120 anatomy
120 resist
(obviously you can drop some points from skills, heal and aatomy especially, to add meditation or somesuch).
The character relies on a perfect weapon, which would, ideally, be high hit spell, hit area, hit lower defence, hit mana leech.
My concept was that you would attack with focus attack every time.
With the right weapon you could be getting 100 mana leech every hit. Hit lower defense would always be up and every hit would use the weapons lightning/fireball. The 100 mana leech should recover most of the cost of the focus attack over time, and with a fast weapon, getting the hit spell every time would rack up damage.
I would run a one handed weapon so that you could throw deadly poisioned shuriken/darts a lot. Throw in deathstrikes to mix things up and you would be golden.
I've tried it out on test shard and it was okay. The problem was I hever had the cash to buy the right weapon. Blaze of death worked nicely (every hit was fireball and fire area) as did the Titan's Leg bone but you could do a lot better with a good crafted weapon, if you can find the right one.
Just a thought.
Also, what about running every dexxer you play with 30 magery and a spell channeling weapon? Then you could fight like a dexxer, but cast clumsy/weaken whenever you like to interrupt any big spells a mage tries to cast. That is purely speculation on my part - never tried it and I don't have access to UO anymore.
