When Pelakka Wurm enters the battlefield, its first ability triggers, causing you to gain 7 life.
Crystalline Crawler triggers, putting seven +1/+1 counters on itself.
Activate Crystalline Crawler's first ability seven times by removing seven +1/+1 counters from it, adding ({4} magic symbol) ({G} magic symbol) ({G} magic symbol) ({G} magic symbol) .
Activate Altar of Dementia by sacrificing Pelakka Wurm.
When Pelakka Wurm dies, its second ability and Enduring Renewal trigger.
Resolve the Pelakka Wurm trigger, causing you to reveal the top card of your library and put it into your graveyard if its a creature card, or draw a card otherwise.
Resolve the Enduring Renewal trigger, returning Pelakka Wurm from your graveyard to your hand.
Resolve the Altar of Dementia ability, causing target player to mill cards equal to Pelakka Wurm's power.
Repeat.
Results
Near-infinite card draw.
Near-infinite death triggers.
Near-infinite draw triggers.
Near-infinite ETB.
Near-infinite lifegain.
Near-infinite lifegain triggers.
Near-infinite LTB.
Near-infinite mill.
Near-infinite sacrifice triggers.
Near-infinite self-mill.
Put all noncreature cards from your library into your hand.