In scenario mode while customizing the 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 can then 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. I recommend you 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 pretty much only with your hero.