Ciarra - Valkyrie
Ciarra is a mid or top lane melee hero with ranged abilities. Her 1st and 2nd abilities allow her to safely last hit in lane and avoid getting harassed too much by the opponent. If she lands her 2nd ability, she can engage with the 3rd ability, freezing the target in place. This allows her to walk around or behind the target and channel her 1st ability.
Ciarra is not a burst melee assassin and instead, more of a DPS hero. She may not be ideal against long range enemies, but will be excellent pick against melee since her passive and 1st ability allow her to safely kite the opponent.
Ciarra shines the most in team fight when a shot-caller is needed. Her ultimate ability, if landed well, along with her 3rd ability, can free the entire enemy team. That gives her team enough team to reposition themselves, chain CC on important targets, or simply retreat from the fight.
She may not have strong CC, but her 2nd ability slow effect is scaled into late game with short cooldowns, so she can stay around the allied carries to slow down the enemies and deal a respectable amount of magical damage with her 1st ability. Her passive should be able to help her scale really well into late game when she can spam a lot of abilities and still have a huge mana pool left.
Her weakness is that she lacks early game damage. In addition, her 3rd ability is her only dash so if she uses it to engage, she will not be able to escape a gank, although it is strongly advised that she should not engage in 1v1 fight early game without knowing the enemy jungler whereabouts.