Path of earthen fury

You gain an animal companion and burrowing speed along with other ability's.

Fury of the earth

Starting at third level when you rage you ignore penalties on difficult terrain and gain a burrowing speed so long as you rage equal to half your walking speed and equal to your walking speed at level fourteen.

Force of nature

Beginning at sixth level once every long rest whenever you would rage you may expend a bonus action to regenerate [roll]4d4[/roll] + half your barbarian levels rounded up for the next three turns.

From below

Starting at tenth level when raging underground with your burrowing speed you may use an action to pull any target down with you the target takes [roll]4d6[/roll] + your strength modifier and is knocked prone and is under full cover however you may attack them.

Indomitable companion

Starting at fourteenth level whenever you may summon as a reaction a companion from any of the following beasts: giant worm, young wurm or a giant serpent Naga when summoned you can take an action as the creatures, but you do not control bonus actions or reactions. At level 18 you can control their bonuses and at 20 you control reactions.