Saheeli, the Sun's Brilliance | Mana Echoes | Hyrax Tower Scout

(and one other card)

Saheeli does not have summoning sickness.
({U} magic symbol) ({R} magic symbol) available, plus an additional ({U} magic symbol) ({R} magic symbol) if you control less than three creatures that share a creature type with
Hyrax Tower Scout.

Activate
Saheeli by paying ({U} magic symbol) ({R} magic symbol) and tapping it, creating a token copy of
Hyrax Tower Scout with haste.
When the token
Hyrax Tower Scout enters the battlefield, it and
Mana Echoes trigger.
Resolve the
Hyrax Tower Scout trigger, untapping
Saheeli.
Holding priority, if you control less than four creatures that share a creature type with
Hyrax Tower Scout, repeat steps 1 through 3 one additional time.
Resolve all
Mana Echoes triggers, adding ({C} magic symbol) for each creature you control that shares a creature type with
Hyrax Tower Scout for each trigger resolved this way.
Activate
Signpost Scarecrow twice by paying ({4} magic symbol) , adding ({U} magic symbol) ({R} magic symbol) .
Repeat.