Water

The only element that never attacks. It heals you on its timer - a share of your max HP on a legendary, a share of the HP you are currently missing on everything else. That distinction matters more than the numbers: missing-HP healing is weak while you are healthy and enormous when you are nearly dead, which makes lower-rarity water pets a genuine comeback mechanic rather than a worse version of the legendary.

Power scales the heal itself, and the side nodes add flat healing on top. The Leviathan, the water legendary, has its own tree entirely, built around trading proc for raw healing throughput and shortening its own cooldown.

Long fights and attrition. Water is close to useless in a fight that ends in four rounds and decisive in one that runs twenty.