1) Immutably 2) In a fixed manner 3) Unassailably 4) Unchangeably 1) Immutably 2) Inevitably 3) Obstinately 4) Unassailably 5) Unchangeably 
[adv] - in an unalterable and unchangeable manner
unalterable, unalterably 1. Incapable of being altered, changed, or modified; inalterable. 2. Impossible to alter; such as, 'the unalterable season of bitter cold in a Siberian winter.'
unchangeably adverb in an unalterable and unchangeable manner; `his views were unchangeably fixed`