Ranni the Witch

Other commanders you control get +X/+X,
where X is the amount of Snow Lands you control

Spells cast with mana generated by only snow lands
also deal X damage to target opponent, where X is
the converted mana cost of the spell cast

Partner (You can have two commanders if both have partner)
"I am the witch Ranni. I stole Death long ago, and
search now for the dark path"