While it's hard to tell what Katara, The Fearless does at first glance without its ability text, she's a 3/3 legendary creature that duplicates the number of triggers Ally cards you control create, allowing for a cascade of abilities during a match
Strength and willpower is more important for non-evasive characters, which tend to get involved in challenges more often
Furthermore, Energy Cards come in several elemental types: Fire, Water, Grass, Lightning, Fighting, Psychic, Dark, Metal, Colorless, and a few special varieties that buck the rules and do something unique instead
When you do, return target artifact card with mana value less than or equal to the amount of life you gained this turn from your graveyard to the battlefield tapped