The Paladin is a hero empowered by the light that protects Human kingdoms. In the single player campaign you can play as two Paladin heroes - Arthas and Uther. Paladin has a very high strength stat and is a melee unit. Paladin primarily uses physical attacks and his abilities do not damage enemies (except for one of them that is used against a specific type of enemy). This is an offensive unit, but with spells that support your troops.
The Holy Light (1) is an extremely useful and most commonly used skill of the Paladin. This spell can heal an allied unit and, depending on the level, restore 200/400/600 health points. A Paladin cannot cure himself in this way. The Holy Light can be used as an offensive ability, but only against Undead units - like the Ghoul, the Necromancer, the Abomination. In this case, instead of healing, it inflicts damage equal to half the health points that would normally be restored. For example, instead of healing by 200 points, you will deal 100 damage points to the enemy.
The Divine Shield (2) is a very unique defensive skill for your hero. When activated, the Divine Shield makes the Paladin immune to all physical attacks, magic, spells and abilities. For the duration of this spell, the hero can attack, move around and use other abilities. During battle, he can attack the enemy without any fear of being defeated. Activate the shield when the Paladin has low amount of health points or you have to retreat from the battle. Each level extends the duration of the Divine Shield by 15 seconds.
Devotion Aura (3) is a passive skill that affects all nearby units. The aura increases the armor level of all nearby units by several points per level. This way you can increase the viability and chances of survival of your troops. It's an extremely useful skill for large armies and it doesn't consume mana points. It is worth adding at least one level of this skill in the first missions of the campaign.