In a comment on Can a pixie levitate on bootlaces carried by a spirit of salzacas?, Simon Withers said
The (at will) Air Spirit Primal Attunement for the Sentinal Druid is a nice replacement for the Prison :)
As fas as I can see, Primal Attunements are
Druid Utility powers available only to Protector Druids, so can't just be swapped in. What am I missing? Is it in fact possible for a Sentinel Druid to gain access to these, or was Simon having a laugh?