15. Chromatic Orb (Wizard Spell)

This spell creates a magical sphere in the caster’s hand, which can then be thrown at the opponent. It is a great First Circle spell, much better than magic missile. Its damage increases as you level up, plus it gets various effects (Blind / Pain / Stun / Burn / Weakness / Paralysis / Petrification / Instant Kill).

Why Chromatic Orb is Great:

• Damage increases as you level up.
• Great additional effects.
• Level 10 and 12 effects completely ignore the target’s Magic Resistance.

Full Spell Details (link)

14. Entangle (Priest Spell)

Although only a first level spell, Entangle is extremely efficient. It immobilizes all hostile creatures within its Area of Effect.

Why Entangle is Great:

• Hostile creatures within AoE cannot move.
• Party members are not affected.
• Can immobilize creatures immune to Web.

Full Spell Details (link)

13. Melf’s Acid Arrow (Wizard Spell)

As the name suggests, this Second Circle spell creates an arrow made of acid and shoots it at the target. Depending on the level, the acid effect lasts between 2 and 8 rounds.

Why Melf’s Acid Arrow is Great:

• Damage over time, unless dispelled.
• Can be used efficiently to disrupt enemy spellcasters.
• Great for finishing off Trolls.

Full Spell Details (link)

12. Mirror Image (Wizard Spell)

Mirror Image basically creates hologram copies (illusions) of the Wizard, thus protecting the spellcaster from any hit – melee, ranged or magical. This is the best protective spell in the whole game PERIOD.

Why Mirror Image is Great:

• Caster cannot be harmed, until all illusions have been hit or dispelled.
• Illusions can absorb any amount of damage.
• Protects caster against physical damage, as well as elemental Area of Effect damage.
• A high-level Wizard can cast the spell as much as four times per battle.

Full Spell Details (link)

11. Melf’s Minor Meteors (Wizard Spell)

Heeey, it’s Melf again, with another awesome spell! When casting this spell, the Wizard creates up to 20 globes of fire and hurls them (quite merrily) at the enemy targets. The globes burst upon impact and engulf the victim in fire.

Why Melf’s Minor Meteors are Great:

• The Meteors strike as +6 weapons.
• They bypass Magic Resistance.
• No save.
• Magic damage + Fire damage.

Full Spell Details (link)

10. Protection from Evil / Protection from Evil 10’ Radius (Priest Spells)

Protection from Evil is extremely helpful, in that its bonuses stack on top of all other armour buffs. The fourth level, 10’ Radius version extends to all party members.

Why Protection from Evil is Great:

• +2 THAC0 penalty to all evil enemies.
• Grants protection from summoned demons.

Full Spell Details (link)

09. Minor Globe of Invulnerability / Globe of Invulnerability (Wizard Spells)

These spells protect the Wizard from magic attacks – the Minor version protects from 1st to 3rd level spells, while the full version includes protection from 4th level spells as well.

Why Globe of Invulnerability is Great:

• Immunity to spells!
• Still lets the Wizard cast spells normally.

Full Spell Details (link)

08. Animate Dead (Wizard Spell / Priest Spell)

Both Wizards and Priests get this spell, and both should use it! It creates undead monsters who serve the caster. This is by far the best summoning spell in BG2.

Why Animate Dead is Great:

• Summoned creatures are immune to most effects.
• Summoned creatures have 90% Magic Resistance, 60% Missile Resistance, 50% Piercing Resistance and 40% Slashing Resistance.
• There is a 5% chance to summon two undead instead of one.
• At caster level 15, this spell summons a powerful Skeleton Warrior.

Full Spell Details (link) 

07. Improved Haste (Wizard Spell)

This Sixth Circle spell doubles movement and attack rates for any creature, with no fatigue penalty. Need I say more?

Why Improved Haste is Great:

• Doubles attack rates.
• Creature with Improved Haste gets a -2 initiative bonus.
• Doubles rate of regeneration.
• Blocks Offensive Spin.

Full Spell Details (link)

06. Cure Wounds / Heal (Priest Spells)

I cannot overstate the importance of healing spells, especially during the early parts of the game. After all, healing is one of the main purposes of a Priest. On a side note, the Cure Serious Wounds spell can be skipped in favour of a more useful Level 4 spell, as it does not make much of a difference from Cure Medium Wounds (see below).

Why Cure / Heal Spells are Great:

• Cure Light Wounds (Level 1): heals 8 hit points and cures intoxication.
• Cure Medium Wounds (Level 3): heals 14 hit points and cures intoxication.
• Cure Serious Wounds (Level 4): heals 17 hit points and cures intoxication.
• Cure Critical Wounds (Level 5): heals 27 hit points and cures intoxication.
• Heal (Level 6): completely heals the target creature and cures all disease.

Full Spell Details (link)

05. Abi-Dalzim's Horrid Wilting (Wizard Spell)

This awesome Eighth Circle spell dehydrates all hostile creatures within its Area of Effect. A high-level Wizard can deal absolutely massive damage with Abi-Dalzim's Horrid Wilting.

Why Abi-Dalzim's Horrid Wilting is Great:

• Does not affect party members.
• 1d8 damage per level of the caster (saving throw vs. spell for half).
• -2 to saving throws for water elementals and plant creatures.

Full Spell Details (link)

04. Dispel Magic (Priest Spell)

Not only does this spell remove magic buffs and wards from enemies, but it also removes all negative magic effects from party members.

Why Dispel Magic is Great:

• If the caster’s level is higher than the levels of enemy casters, it removes all effects, regardless of spell level.
• There is only one way to block this spell (by pre-casting Spell Immunity).

Full Spell Details (link)

03. Minor Sequencer / Spell Sequencer (Wizard Spells)

Spell sequencing is truly powerful stuff. It enables the Wizard to store and cast two (Minor version) or three (full version) spells simultaneously, by means of the special ability button. All the spells must be level four or lower.

Why Sequencers are Great:

• Create spell combos and unleash them on your enemies.
• Zero casting time.
• Colourful combos make for spectacular gameplay. Be creative!

Full Spell Details (link)

02. Chain Contingency (Wizard Spell)

Chain contingency works like an algorithm – you pick three spells, which will be cast when a certain condition is met (e.g. the Wizard sees an enemy, the Wizard is hit by an enemy, the Wizard has lost 50/75/90% of hit points, the Wizard has been poisoned).

Why Chain Contingency is Great:

• Casts three spells simultaneously.
• Can pick spells up to (and including) level 8.

Full Spell Details (link)

01. Summon Planetar (Good / Neutral Wizard Spell) or Summon Dark Planetar (Evil / Neutral Wizard Spell)

This spell (predictably) summons a powerful Planetar. Just cast and enjoy as he tears your enemies to shreds!

Why the Planetar is Great:

• Immune to Fire / Cold / Electricity.
• 75% Magic Resistance, 50% Magic Fire Resistance, 100% Magic Cold Resistance, 10% Resistance to Slashing, Piercing, Crushing and Missile damage.
• Has regeneration.
• Casts spells.
• 2d10 + 3 slashing damage.
• On-hit 25% vorpal.
• On-hit Dispel, level 15.

Full Spell Details (link)

Also Be Sure To Read:

• [Top 10] Baldur's Gate 2 Best Companions And How To Get Them
• Baldur's Gate 2 Best Class - What To Pick
• [Top 15] Baldur's Gate 2 Best Spells
• [Top 5] Baldur's Gate 2 Best Builds
• [Top 10] Baldur's Gate 2 Best Weapons And How To Get Them