Illumination: 20-100% Chance to regain 60% of mana spent, if used to heal a party member, after scoring a critical hit.
Holy Power - Increases the critical effect chance of your Holy spells by 1/2/3/4/5%.
Holy Guidance - Increases your spell damage and healing by 7/14/21/28/35% of your total Intellect.
Benediction - Reduces the mana cost of all instant cast spells by 2/4/6/8/10%.
Conviction - Increases your chance to get a critical strike with all spells and attacks by 1/2/3/4/5%.
Sanctified Seals - Increases your chance to critically hit with all spells and melee attacks by 1/2/3%.
Tips and Tactics
Holy Shock is a unique instant cast spell, obtained through the Holy tree. It can be used either as a "clutch" heal or a powerful "nuke" spell. It is one of the last talents in this tree, so prepare for a serious commitment to get this. You can use it with Divine Favor to gain 100% critical chance. Note that the Illumination talent will refund 60% of the mana cost of the spell when a critical heal is obtained, but not when the spell is used offensively.
It is even less mana efficient than Holy Light and so should only be used when an instant cast is essential or you risk burning your mana too fast. Flash of Light is the most mana efficient Paladin healing spell.
It may look useful for pulling. However, properly specced Protection paladin tanks can rarely spend so many points into Holy tree to get it.
As a spell from the Holy School, using it offensively with Righteous Fury can generate needed aggro when off-tanking as a Holy paladin. A quick jolt of holy energy with at least 160% aggro generation will grab attention. Again, normally Protection paladin tanks do not have it.
This ability was present in Warcraft 3 under the name of "Holy Light" and was available to paladin heroes.