Imagine the Above Poster as a Summon/Esper/Aeon/GF/Whatever!!!!

[Rocket Edge]

Shiva. ^

[Twilight Edge]

Traffic=vehicle.

Doomtrain.

[Vivisteiner]

Yojimbo.

Because Sephy has a big sword tha annihilates all - Zanmato
And Yojimbo appears at around 'Twilight's Edge' in the summoning animation.

[Evastio]

You'd probably look like some spikey (because of Cactuar Avatar) monkey and all of your spikes (Spikes=Swords=Steiner) would be different elements (Different Elements=Spells=Vivi). You'd roll into the enemy, shaking the ground and hit them with all of your elemental spikes. Your summon would be called "Elemental Earthquake".