Guide of Souls becomes stronger with other energy cards, but I wouldn't consider them a necessity, especially in Commander
Maybe it is the cool spacecraft and warp cards that allow for easy double spelling, or perhaps the kavu are fascinating
Creatures (21) 3 Archangel Avacyn 2 Selfless Spirit 4 Depala, Pilot Exemplar 4 Aerial Responder 4 Fairgrounds Warden 4 Veteran Motorist Planeswalkers (4) Lands (24) Spells (11) Toolcraft Exemplar might seem like an obvious missing card, but I didnt want to include too many juicy targets for the +1 ability of Liliana, the Last Hope
The effect is worth it at the beginning of most games
See this article to learn why classic fast-mana card Mana Vault has tripled in price, following an update to the MTG Commander banlist
Anything in here that I missed or that you'll try out in your next brew