WotC was very concerned that pushing this mechanic too hard could lead to repetitive and unfun play patterns, so the majority of venture cards were scaled back in power pretty hard
The lower in power level a Cube gets, the more that 3/3 body matters, and just keeping the menace token is also of some value in these contexts
Once certain conditions have been met, your card flips over to reveal a (usually nastier) alternate form
Although you don't want loads of non-mill cards I think a smattering of the best not only improves the overall potency of the deck but also improves the goldfish clock
Seedglaive Mentor is strong enough to pull you into the Mouse archetype, but Im not a big fan of Veteran Guardmouse
Pillar Analysis: Unique Effect (Creature Lock), Scarcity (Legends, Reserved List), Control Staple