You will encounter Mountain King at the end of the Human campaign. It's a dwarf warrior, determined to fight. It's a very offensive character that focuses on melee combat, although some of his skills may indirectly support your army. Most of his skills allow him to stun or slow down enemies, which is very useful and almost impossible to block. His main statistic is strength, so over time he becomes an extremely tough hero. A high-level Mountain King is able to defeat a few weaker enemies alone.
Storm Bolt (1) is the first skill you should choose when you start developing this hero. It inflicts significant damage and at rank 3 is able to defeat weaker support units with just a single blow. Use it to attack ground and air units. Additionally, each bolt stuns the enemy for a few seconds. Stun is the most useful part of this skill. This way you can exclude the strongest enemy, hero or spell-casting unit (especially these with many abilities or spells) from combat. Only a few enemies are immune to stun, so it makes this skill very useful. It is worth to quickly develop this skill to rank 3.
Thunder Clap (2) is an area of effect ability - it slams the ground, damaging nearby enemy units. It deals damage to all enemy ground units, and applies a slow effect. Units affected by this state have half the movement and attack speed. It is worth sending the Mountain King to battle with melee units and use this skill. Thunder Clap is useful, but there may be situations when you won't be able to use this ability effectively.
Bash (3) - is a passive skill of the Mountain King. It only applies to the hero, but does not use mana and works all the time. The dwarf has the chance to deal additional damage and stun the enemy with every physical attack. The higher the level, the better the chance to stun the target. This ability makes the Mountain King a dangerous opponent, and the stun can stop even the strongest enemies. It is worth noting that the Bash cannot be blocked by units that are immune to spells, although it still won't work on units that are immune to stun.
Avatar (4) is the ultimate ability of the Mountain King. When this spell is activated, the hero turns into a stronger character. He gains additional health points, damage and armor bonuses for a short time. What's more, in this form the Mountain King is immune to spells and can still use his skills. It is worth using the Avatar during large battles or when the Mountain King has to fill the defense gaps and face strong enemy units.
Resurrection (4) is the final skill of the Paladin. Once activated, you resurrect and revive up to 6 dead allied units lying near the hero. The strongest units return to the battle with maximum health points and can take part in it immediately. Important! The Paladin must be near the bodies of your fallen warriors. Therefore, when fighting against the Undead, it may turn out that the bodies were eaten or used to summon skeletons. During larger battles, it is worth not to use Holy Light to heal your units, but to save mana for resurrection (especially since it will be very expensive to heal stronger units). Then it is worth throwing your troops into a suicidal fight, and then resurrect the strongest units and tip the balance of victory to your side.