Generally you want to make sure you have a two or three-color identity for a theme like this, and remember that the majority of your good enablers will be in Grixis colors: Brallin, Skyshark Rider plus Shabraz, the Skyshark Raffine, Scheming Seer Chainer, Nightmare Adept Rielle, the Everwise Soul of Windgrace Amber Gristle OMaul plus Agent of the Shadow Thieves (or Criminal Past) Slogurk, the Overslime Despite their contrarian approach to the Commander metagame, discard decks are capable of some truly disgusting lines and offer a huge range for individual expression
A 4-mana 3/5 that grants haste to everything is pretty good, and sometimes Tannuk will let you Warp stuff
Had this been a simple modal card, it would be remarkable for its flexibility, but you can have both for the low, low cost of controlling your commander
With every deck you'll also get 10 Planechase cards that will transport you to your favorite places throughout time and space in the Doctor Who universe
No blue though, so thats a knock against it
But maybe Wizards of the Coast has a curveball in store