Reanimator decks typically use removal-resistant cards like these along with a whole host of cards that come back from the graveyard, making it almost impossible for opponents to remove their threats
You can drop her, and then when you need, monstrous her up
Some instants can be used to counter another spells, to destroy a creature, give the power and toughness of a creature a boost, ect
This situation doesnt come up that often though, which is why I valuable Night Whispers flexible mana cost over Sign in Bloods ability to target other players
With Elven Council being only 2 colours, it makes Mana fixing a lot more easier, solving a potential bugbear for new players
If that wasn't enough, if you cast a spell which is multiple of these MTG colors, you get each of the abilities that share a color with the card cast