Agni's core gameplay revolves around ticking damage and interplay between his abilities. His first ability, Noxious Fumes, allows him to place a damage-over-time field on the ground, which he can ignite with any of his other abilities. He also gains a buff to set enemies ablaze with his spells after landing several normal attacks. With a combination of mobility, area effects, and steady burns, he seems the sort to play if you enjoy laying a burning field of destruction... but perhaps you should check the video past the cut to be sure.
[Source: Hi-Rez Studios press release]