Earth spike(-s)

When this spell it's being casted, 1 wild Earth spike emerges from the ground in the closest area of the enemy you've chosen, just to provoke [roll]1d6ad[/roll] bludgeoning damage or [roll]1d8ad[/roll] piercing damage.

The enemy must throw [roll]1d20[/roll] on DEX savingthrows to avoid the damage and also avoid the loose of the equilibrium ( an extra damage can be applied here, but not sure what dice I could use here ).

Each 2 spell lvls above lvl 2 you cast this spell, 1 more spike it adds ( plus the probability to improve the spike/-s size in an idem no bigger than 16.40 ft. )