Although categorized as a tank Grakk can either be played as a support or a mage carry depending on the team composition.
Passive - Blood Ritual
Whenever Grakk takes damage equal to or more than 10% of his current HP he triggers an explosion dealing magic damage to surrounding enemies this passive has a 2-second cooldown. Blood ritual will also activate upon Grakks death dealing extra damage. Therefore Grakk can collect kills even when he is dead.
Ability 1 - Earthquake
Grakk stomps the ground dealing magic damage and slowing surrounding enemies. The damage and slowing effect are doubled when enemies are close to Grakk. Due to its low cooldown, Grakk can also use earthquake frequently to slow his foes.
Ability 2 - Devils Chain
Grakk throws a chain hook to pull the first enemy hit towards him. Additionally, whenever Grakk scores a kill or assists he will gain 125 points of maximum Hp up to a maximum of 20 stacks. This directional skill is Grakk's main control ability.
Ultimate - World Devourer
after a short delay, Grakk disables all enemies in front of him and continuously drains away their HP while gaining a temporary shield. This is an AoE crowd control skill that can effectively help Grakk's team win team fights.
To deal maximum damage first pull the enemy with devils chain then slow him with earthquake, followed by world devourer to complete the kill. However, sometimes earthquake and Devils chain is all it takes to score the kill.
To effectively control the enemy approach him and use earthquake first then use world devourer to disable and damage the enemy. Once the enemy tries to escape use devils chain to pull them back and score the kill. Alternatively, Grakk can initiate with devils chain and follow up with earthquake.
Overall, Grakk has the combination of formidable control abilities and incredible damage allowing him to turn around battles at ease.
Grakk was known for his brutality. As the executioner, he shackled imprisoned souls, and tore open the offending souls with his teeth to torture them. He had to pay a steep price for this though. The price was that he could no longer digest any food other than souls. He needed to devour souls to satisfy his constant hunger.
To stave off hunger during times of peace, he had to ask for help from Zephys and Nakroth; the former harvested souls while the latter past judgment. All guilty souls became his food. After the war broke out, in return for Grakk's strength, Maloch promised Grakk that he could do whatever he wanted with the enemies he captured.
The never-ending feast turned Grakk into a war maniac. With every fresh soul consumed, his power grew. He turned all of the things he could not eat into the Fallen to capture more food for him.