One thing not to underestimate about casualty is that only half of the effect will be stoppable by a regular counterspell, which gives the casualty spells in general some added reach in metagames heavy on counters
Their colorless nature enables them to fit into any deck while offering strong synergy with mana ramp and sacrifice strategies
Best Cards Thespians Stage: The premiere utility copying land, Thespians Stage is a strong card in land focused decks by becoming an extra copy of whatever land you want
Random Encounter This sorcery costs six in Red and then has flashback for eight, and then shuffles, and then mills four and drops all dorks milled with haste to kill that turn
The only problem with this win, besides it being undeterministic, which is on purpose, is the sequence of actions it creates can be pretty tough to follow
It fits well into a lot of different subcultures