Protection spells are important to keeping Orvar around, and there are plenty of excellent choices
However, the real strength of Katilda lies in the fact that they give every Human you control the ability to tap for one mana of their colors
Here's a short list of great ones: Anger, Flamekin Village, Hall of the Bandit King, Hammer of Purphoros, Fervor, In the Web of War, Ogre Battledriver, Urabrask the Hidden The Party Doesn't Stop You can end up dumping your hand pretty fast with Rakdos, so it's important to have multiple ways of refilling your hand
Where WotC says wildcard value, rest assured that it means the most marked up value possible for the gem-equivalent of the wildcards
Lifelink decks can use this enchantment to that end, but it also strengthens another key resource: your life total