Wraith and Spectres (which were called nightmares, before the resource was added) predated Phantasms significantly. I believe they date back to Light, while Phantasms (and the whole Shadow sphere) were only introduced in Shadow. I think that means they were the shortest lived summon.
Guardian Vines are actually still in the game, but I don't think there is any way to get one without cheating. I'll probably add them back in my version, and maybe give them come poison strength and the ability to cast Entangle. I'm thinking they may be the Nature III spell, while Vitalize gets a delay and moves to Nature II (unless I decide it goes better in the Creation Sphere). (I'm thinking Poison Blade will be a Nature I/Shadow I cross sphere spell.)
And of course the Azer is still around though an event, Griffins are now normal animals, Imps remain as UUs, and Chaos Marauders are still a planar gate unit.