Spells

Rowan continued stabbing and slashing at the regenerating body of Thenos mechanically, inside the Wooden Fortress, the corrupted titan's essence could not escape and if Thenos did not take a corporeal form, his stores of energy would be consumed faster than normal, because this fortress also drained energy from Thenos and only in his corporeal form could he fight against this drain to a certain extent.

There were many complicated moves Rowan could have used that would damage Thenos far more quickly, but in this situation, simple attacks were the best strategy to use, and if he knew Thenos, then he was most likely hiding the greatest of his weapons until he was desperate.