I find the sentinel LoL underwhelming. His basic attack is good enough, but everything else is kind of bad. He can't cleanse or heal. His force and titan shield are easily removed by most of the characters in the arena and sleep is not that great because of limited number of sleep supporting Eddies. His passive simply grants some immunities that are also provided by some 4 star characters like sentinel bomber boy. He is probably the worst LoL. I recommend getting him only after getting all other LoL's for dark lilith achievement.