If i mount Raptor Herder and then dismount it will it summon another Raptor Hatchling?
Apr 04, 2019 PDT
No, because it comes back into play exhausted.
Basically, if your ally has a trigger when it leaves play (like Sun Sister) you can trigger it when mounting. As doktarr#0a=m mentioned, though, none of the "comes into play" abilities will trigger when dismounting due to the exhaustion (it comes into play exhausted rather than coming into play, then getting exhausted).
the exception to the rule is iron worker and temple elder whos come into play effects are inexhaustable, so still trigger.