Only two strike me as real possibilities based on the double theme, and that's Kiora, the Crashing Wave and Narset Transcendent
The great thing about pendulum decks is that when theyre destroyed or tributed, they get set face-up to the extra deck where they can be pendulum summoned all over again
Next we have a card that upon destruction, sort of turns into an elf of your choice: Then we have a creature that gets better as certain creature types show up: Unlike most of the tribal things in this set, note that the Golem only cares if you control the specified critter
Its kind of a home base for Magic, full of many forms of recognizable fantasy flora, fauna, and humanoids
Shiko, Paragon of the Way Part of my excitement for Shiko, Paragon of the Way is that I want it to be good in Jeskai decks