Destructive Magic

From the official site: The School of destruction manifests as blasts of pure destruction. Most of the spells aim at dealing damages or causing destruction, at an high extent. These spells are based on Ice or Fire components.

Amongst those spells, you will find chain lighting spell. It causes magical elemental damage by lightning to four units, starting with the targeted stack then spreading to the nearest ones on the battlefield, including friendly troops. The farther the unit is positioned on the Initiative Bar, the less damage it suffers. This spell is great when you have enemies you cannot reach or when you have creatures with low initiative that stand far away on the Initiative Bar(Golem or Treants for instance).

Eldritch Arrow

• Shoots several magic missiles to deal non-elemental damage to the selected
  enemy creature. Higher Spellpower increases damage. The number of
  missiles fired depends on hero level.

Cost: 4

Stone Spikes

• Deals earth damage to all creatures in target area (cross form)

Cost: 5

Lightning Bolt

• Deals lightning damage to selected enemy unit.

Cost: 5

Ice Bolt

• Deals ice damage to selected enemy

Cost: 6

Fireball

• Deals fire damage to all units in the target area.

Cost: 6

Circle of Winter

• Deals ice damage to all units surrounding the target spot.

Cost: 7

Chain Lightning

• Deals massive lightning damage to several adjacent creatures, starting with
  the selected one. Higher Spellpower increases damage. Jumps to four units,
  halving damage each jump.

Cost: 8

Meteor Shower

• Deals massive earth damage to all creatures in target area.

Cost: 5

Implosion

• Deals earth damage to a single targeted enemy unit.

Cost: 5

Armageddon

• Deals massive damage to all creatures and war machines on a battlefield.

Cost: 12