Heidi, Follower of Heroes

First Strike, vigilance
Oath of Devotion -- Whenever one or more creatures you control deal combat damage to a player, instant and sorcery spells you cast cost {1} less to cast until your next turn.
Remove a loyalty counter from a planeswalker
you control: Add {w} or {u} to your mana pool.
"The most heroic leaders are true to us."