flames, blaze
焱 centers on intense, active fire: a blaze or leaping flames. It emphasizes the visual and energetic quality of fire rather than a single flame.
焱 is formed by tripling the fire radical 火 to intensify the idea of fire, suggesting a large blaze or many flames. This reduplication pattern is a known way to express intensity in Chinese characters.
Three fires stacked together: one fire on top of two more fires. That much fire can only be a roaring blaze.
For エン, picture a huge blaze that looks like the end of the world: end -> エン, and the triple flames consume everything.