To determine which option is not an instrument used to evaluate the quality or characteristics of a learner, we need to understand the purpose each instrument serves in the context of educational assessment and evaluation.

1. Rating Scale: This tool is used to assess the degree to which a learner exhibits certain characteristics or performs specific tasks. It provides a quantitative measurement through ratings, which can be numerically scored.
2. Checklist: This is a list of criteria or behaviors that the learner should exhibit. It helps in objectively determining whether each item on the list is present, thereby assessing the learner's performance or characteristics.
3. Rubrics: A rubric is an assessment tool that outlines the criteria for evaluating a learner's performance and the levels of quality for each criterion. It provides detailed descriptions for what is expected to achieve different scores, ensuring a qualitative assessment of work.
4. Inventory: Generally, an inventory refers to a list or record, typically of stock items. In an educational context, a personality or interest inventory may be used, but it is not directly employed to evaluate the quality or characteristics in terms of performance criterion, unlike the other tools listed.

Conclusion: Among the given options, an "Inventory" does not serve as a direct tool for evaluating the quality or characteristics of a learner's performance in the way that a Rating Scale, Checklist, or Rubrics do. Therefore, the correct answer is Inventory.