Only cards that were or could have been legal on Type II/Standard on some time (that includes pre-banned cards like Sol Ring).
The drive is to have a powerful format but without the broken or too pushed things from special sets like MHx.
Magic 2010 brought many changes to Magic regarding design of core sets and rules changes, but not many cards for a cube like this survided these days, even though they were staples in their time.
Legal Sets