Talk:Endless Defense/@comment-84.85.99.117-20130822133359/@comment-178.140.13.150-20130822185648

Look closer. For example, Kiliken starts with Tier 1:

5 wave - Tier 1;

10 wave - Tier 2;

and than:

15/20/25/30+ wave - Tier 3.

So, yeah, "all tiers of keys can be acquired from tier 1 defense missions"