They dont let you cast a big spell for free or give you extra turns, but they do the dirty work that is necessary in Commander decks they make your mana way better
For example, it is possible at any excavation point in the combo to not reveal any eligible monsters that can be summoned, something that can cripple the Deck from as early as step 2
If you dont see this as the centerpiece, then the fact that its cost is very flexible should still make Oona a very desirable card for some control and mill decks
Now I dont think Setzer is that powerful on his own, and really I cant get too excited about a Rakdos pilot that spawns a pretty average vehicle
And with the release of Time Spiral (2006), Threshold was retroactively changed into an ability word, and all previous cards were given an errata so that "Threshold -- [effect]" now read essentially as a reminder of the condition while also aligning it with other ability words like Metalcraft ( which cares about having three or more artifacts ) or Morbid ( which checks if a creature died this turn )
