To start
Commence
Allowable
Permissible
To reduce or damage in quality or worth.
Deteriorate
Incapable of change.
Invariable
Choice of one of two options
Alternative
Watch kept while others are normally sleeping.
Vigil
Not aggravating but not interesting.
Bland
Watchful for danger or error.
Vigilant
Bottomless pit
Abyss
Persistent in harshness or severity.
Relentless
Daringly, often recklessly adventurous.
Audacious
Exceptionally steep.
Precipitous
Planned or accomplished usually by many people
Concerted
To lure or entice by deception.
Decoy
To originate or send out from a source.
Emanate
Possessing a friendly manner or temperament.
Genial
To judge or conclude based on guesswork.
Conjecture
To keep something desirable visible but out of reach.
Tantalize
Facial expression.
Countenance
To firmly plant or establish.
Engraft