You designate one creature within 60 feet and speak aloud the true name of the beastly arth, which appears next to the target in an unoccupied space and attacks it immediately. On subsequent turns the arth shares your initiative but acts immediately after you. On its turn, it attacks the designated target to the best of its ability. It always knows the direction to its target, the target cannot hide from the arth, and the arth has advantage on saving throws made against affects originating from the target. The arth disappears if it's reduced to 0 hit points, its target dies, or the spell ends. The summoning cannot be dispelled and the arth cannot be banished for the duration of the spell.

If you stop concentrating on this spell before it reaches its full duration the arth does not disappear but is no longer under your control. It immediately rolls a new initiative and switches its target to you.