User blog comment:Starchythepotato/A Quick Arena Guide/@comment-172.56.39.6-20141210074047/@comment-50.155.60.99-20141222153418

Thing is, these are fairly common units; infact, it's old enough that it only takes into account 5* units, missing a lot of info that came after September from recent patches.

If you're bothering with arena and you have none of these units, you're either doing terrible rare pulls or you're not doing it right (not rare summoning/ plaing arena with no units).