Ragnar Goliaths unlock at Castle LVL. 12
These can be a bit of a tricky one. Un-boosted they're too slow to be effective against a sizeable set of ranged units, and they will constantly get wounded enough to die during a fight on the attack. Boosted, however, especially in toughness, they can be a powerful force that can bull through quite a bit. Berserker titans are not good to pair with them, but good Guardians or Rangers are a viable option for both attack and defense.