In scenario mode, when you use a customized leader give him Atk 7, Def 7,
Dmge 6, and Life Stealing. He does not need anything else. Note: This is 
for a dwarf; other leaders might have 1 or 2 points difference on Atk or 
Dmge; do not get rid of Life Stealing or Def. You should also give him 
the following spheres: 4 Air, 3 Fire. Air has Chain Lightning, Haste, and
Windwalking. Fire has Fire Halo and some good offensive spells. Attack 
enemies with your hero, He will be able to destroy almost anything. When
he levels up, give him full Def then Wall Climbing and Round Attack. Do 
not give him Archery or some form of a ranged attack, because in automatic
battles he will use those and Life Stealing will not do anything. It is 
the most important thing about the leader. When your leader has full Def
and Wall Climbing, give him better Atk, Dmge, and Resistance. At about 
level 11, your leader will be strong enough to take on groups larger than
15 and leader's bases. You should also give him abilities like Extra Strike
and Parry later. Remember, spellcasting is not a large part of this leader.
The best place to use this leader would be Oracles Eye, because there are 
plenty of opponents. At the end of the scenario your leader will be 
slightly higher than level 20. Remember to attack almost only with your
hero.