Lady Rime is a legendary frostling hero that gains strength the more mana you spend on her. Her strength and ability can be upgraded when she is leveled up. Lady Rime is found in ramp and control decks.
Lady Rime is a strong unit that starts off weak and grows in strength as you have more mana.
Lady Rime's ability can be controlled somewhat by playing her last, as to save mana for your other cards.
Dawnsparks, Frozen Core, and Gift of the Wise can all generate more mana to power Lady Rime. If you do not rely on mana-generating cards, Lady Rime still eventually gains more and more strength as the game goes on.