Using an indestructible creature to block a lifelinker will still result in the opponent gaining life, and blocking a creature with wither will still cause -1/-1 counters to be placed on your creature (which could actually kill it!)
This is because certain cards do essentially the same thing, but at different time scales: Some exile the permanent, and then return it to the battlefield straight away
Gamechangers for a Sauron deck The Ur Dragon The Ur Dragon offers a simple strategy, but it's still powerful enough to stampede casual commander tables (and steal a few more competitive wins, too)
Survival At the beginning of your second main phase, if Cynical Loner is tapped, you may search your library for a card, put it into your graveyard, then shuffle
This card lets you mill two cards at the beginning of your upkeep