Nisalt is interesting but not exactly useful in most places. He creates magic vials and then throws them to inflict burning or poison. These can combine to create a unique burn but you have no control over which vial he throws. He also boosts his damage based on the vials he has recently made and his ultimate speeds up their creation. In the right codex Nisalt is an amazing choice, but his kit revolves around rng making him inconsistent elsewhere.