public function highestOnChain($achiever)
    {
        $latestUnlocked = null;
        foreach($this->chain() as $instance) {
            /** @var Achievement $instance */
            /** @var Achiever $achiever */
            if($achiever->hasUnlocked($instance)){
                $latestUnlocked = $achiever->achievementStatus($instance);
            } else {
                return $latestUnlocked;
            }
        }
        return $latestUnlocked;
    }