Each race has its own dedicated Element. 

Elithen – Ice
Mossmane – Poison
Ragnar – Earth
Unak – Fire
Human – Physical
Vikings - Lightning
This means that each race will use one Element to fight with. For an example, the Elithen will shower their foes with Ice and wield Frozen weapons.

Elemental dame also means that some Titans will be weak to some Elements. You can give your Titans Relics to boost resistance to certain elements.

The only exceptions to this are the Unak Boar Titans (Venomtusk, Snowgore and Flamehide)