Its more a commitment to mana ramp than anything else
Venser also has plenty of extra support in Phyrexia: All Will Be One from cards like Staff of Compleation, which appreciates the incidental Lifelink, and Scheming Aspirant, which helps you snowball even faster
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Good sacrifice targets usually fit one of these categories: Enters value: creatures like Solemn Simulacrum or Elvish Visionary that already replaced part of their cost Dies value: creatures with death triggers, recursion, or graveyard payoffs Mana value 3 or 4 creatures: these create the best early Emerge curve Artifact fodder for Emerge from artifact: eggs, Wellsprings, Clues, Blood tokens, and similar pieces Recursive creatures: threats that come back from graveyard or exile Creatures you wanted in the graveyard anyway: because some decks treat the graveyard like a second hand with worse lighting The practical sweet spot is often mana value 3 or 4
But every Commander play group needs at least one player with a shrines deck
The exile ability that allows you to play cards you cast from exile along as you attacked with Ur-Dragon...?`Yeah, I don't feel that's considering that you are play Ur-Dragon