Ice Block

Ice Block is a level 22 mage spell that gives short-term immunity to all damage and attacks (except priest's Mass Dispel), at the price of being able to take no action. Ice Block also purges most debuffs.

Using Ice Block debuffs the mage with Hypothermia for 30 seconds, which prevents them from using Ice Block during that time. The effect is similar to the paladin debuff Forbearance.

"Ice Block" is often used as a verb, meaning to use Ice Block to avoid an attack, as in "I Ice Blocked that rogue's Envenom." When Ice Block is used to remove a debuff, it is commonly referred to as "Ice Blocking out of ~", as in "I Ice Blocked out of sheep."

Improvements

 * Cold Snap (Frost) - Resets the cooldown on Ice Block.

Talents

 * Glacial Insulation (Frost) - Ice Block casts Ice Barrier on the mage when it ends.

Tips and tactics
Ice Block is useful for escaping from incapacitating effects and crowd-control spells, waiting for your cooldowns, blocking a large single-hit attack (such as Pyroblast), or buying time for a healer to heal you.

In a one-on-one battle, Ice Block may give your opponent time to cool down abilities, heal, or run. You should rarely let Ice Block expire on its own, but instead cancel when the timing is right, usually immediately after casting.

Ice Block can be used to avoid fall damage (see Blink and Slow Fall (ability) for other ways). While Ice Blocked your character falls normally, but doesn't take any damage when hitting the ground. (In previous patches, an Ice Blocked mage would hover in the air, then begin to fall when the spell expired.)

Ice Block will prevent drowning and fatigue damage, and reset the damage counter (not the bar) to zero. You will still lose breath and become fatigued while Ice Blocked.

Ice Block is powerful enough to remove almost any debuff, including Living Bomb. Some notable exceptions are Resurrection Sickness, Vaelastrasz's Burning Adrenaline, Deathbringer Saurfang's Mark of the Fallen Champion and the Deserter debuff from battlegrounds.

Contrary to popular belief, Ice Block will not reduce your current threat level. The reason for this misunderstanding is that enemy AI is programmed to ignore you if you are invincible and move on to the next-highest target on its hate list. As soon as the effect fades the enemy may resume attacking you. However, it will prevent you from performing any actions that generate threat, allowing others (who are still attacking, healing, etc) to rise ahead of you on the mob's hate list. Use Invisibility to remove threat.

Using this macro a mage can instantly stop casting a spell and ice block to protect themselves with no delay. This makes it very useful in PvP or PvE situations which requires you to have fast reflexes to a changing situation.

/stopcasting /cast ice block

Trivia

 * Ice Block is an epic Mage spell in Hearthstone. The flavor text reads: "Ice is nice, and will suffice!"
 * This spell has been used several times in the lore, but very rarely. Khadgar uses it to protect himself from on, and again against Gul'dan within the Tomb of Sargeras. Several formerly captured magi use it to shield themselves from Sindragosa in the Pit of Saron after the defeat of Scourgelord Tyrannus.