Spell Shield

Spell Shield is a generic Talent that grants a nice chunk of Spell Armor for a short duration upon being hit. It can be toggled on the hotbar, so you can choose when it will protect you. It is a nice defensive option, if you are up against a team with high amounts of burst damage because it can halve the damage you take, being particularly effective against Heroes like Zeratul or Nova whose attacks may be hard to predict. It is similar to Spell Block effects in that it automatically triggers upon incoming damage, but varies from it in that it lasts for a duration rather than blocking specific instances of damage.

Mechanics
Spell Shield can be instantly toggled between active or inactive on a 0.5 second cooldown, but it cannot be toggled while on cooldown after being triggered. Spell Damage that is unaffected by Armor cannot trigger an activated Spell Shield.

Spell Armor from Spell Shield does not stack with other Armor effects.

Old versions
Initially Spell Shield granted up to two charges of Spell Block, reducing their damage of a single enemy Ability by 50%.

Base version

 * Kharazim
 * Uther
 * Zagara
 * Zeratul

Modified version

 * Lunara's level 13 Talent, "Greater Spell Shield", grants 75 Spell Armor for 3 seconds upon triggering on 30 second cooldown.
 * Thrall's level 13 Talent, "Spirit Shield", grants 50 Spell Armor for 2.5 seconds upon triggering on 45 second cooldown, which is reduced by 10 seconds upon triggering Frostwolf Resilience.

Removed
These Heroes no longer have Spell Shield as a Talent option.
 * Anub'arak
 * Arthas
 * The Butcher
 * E.T.C.
 * Johanna
 * Kael'thas
 * Leoric
 * Lt. Morales
 * Muradin
 * Murky (old version)
 * Nova
 * Rehgar
 * Sonya
 * Stitches (old version)
 * Sylvanas
 * Tassadar
 * Valla