These are some tactical spells I'd like to see that require code:
Reflect - Upon being hit by an offensive spell, that spell is reflected back to the caster. After the spell is reflected, the unit that avoided the spell loses 50% of its spell resist for 3 turns. For AOE spells, other friendly units would still get hit, the reflect would make only the caster suffer.
Essence Trap - Each time this unit is hit by a spell it gains 5 mana and gains +2 Initiative for 5 turns. The effect does not stack with itself.
Lord of Currents - Each time target casts a spell it gains +10 resistance to either fire, cold, poison or lightning. It also increases spell damage by 10%. The temporary effect lasts 3 turns, and stacks with itself.
I'd also like to see tactical-wide weather changes. Only ONE of these spells could be active at once, casting another one would instantly dispel the previous. You could very sparsely use particle effects, but the primary visual effect would be from the camera lightning already implemented.
Fog - All units lose 20% of their current dodge and accuracy. (favors tank units)
Ice hail - All units take 3-6 cold damage each time they act. (favors slow units)
Acid rain - All units lose 25% of their current defense. Poison resistance mitigates this effect, a unit immune to poison damage suffers no ill effect.
Grand Sealing - All summoned units suffer 3-10 damage each time they act. All other units gain +10 Spell resistance
Eternal Night - All ranged units lose 40% of their accuracy.
Mud rain - All mounted units lose 1 Moves.
Starshine - Current weather effect dispelled.
Dawn of the Dead - Whenever a humanoid unit dies, it is replaced by a skeleton carrying roughly the same equipment. The skeleton is a Monster and will attack anyone who belongs to a faction.
Chaotic Realm - Each time any unit is hit by a ranged or melee attack, or a spell, a random effect is rolled on that unit. Effects vary greatly, such as taking damage, getting healed, gaining temporary or permanent stat boosts, losing stats temporarily or permanently, losing items, teleported around the map and so on.