If I had no allies with the X-Factor, X-Force or X-Men traits in my deck would I just discard until I went through my deck? Adam Warlock could benefit quite nicely from that with Soul World if so. Just a thought.

Caliban is a solid ally with a Call for Aid-style response upon entry. This can be used in a few different ways - it can find a specific ally your deck is built around like Fantomex if that's the only target, it can load up your graveyard to increase the versatility of Make the Call, or it can activate Digging Deep/White Fox, which is a very strong use. Even without a combo, it's above rate for a 3-cost ally due to drawing a card when it comes in. The psionic trait also makes Caliban premium for psionic-theme decks. A very nice card!