The Chain Veil + Ashnod's Altar + Teferi, Who Slows the Sunset + Elspeth, Sun's Champion
The Chain Veil
Ashnod's Altar
Teferi, Who Slows the Sunset
Elspeth, Sun's Champion
Infinite activations of most planeswalkersInfinite colorless manaInfinite creature tokensInfinite death triggersInfinite creature ETBInfinite lifegainInfinite lifegain triggersInfinite creature LTBInfinite mana creatures you control can produceInfinite mana lands you control can produceInfinite mana permanents you control can produceInfinite creature sacrifice triggersInfinite untap of creatures and lands you control
How it works
Activate Elspeth's first loyalty ability by putting two loyalty counters on it, creating three 1/1 Soldier creature tokens.
Activate Ashnod's Altar twice by sacrificing two Soldiers, adding CCCC.
Activate The Chain Veil by paying 4 and tapping it, allowing an extra activation of your planeswalkers' loyalty abilities this turn.
Activate Teferi's first loyalty ability by putting a loyalty counter on it, untapping The Chain Veil and up to other other creature and/or land you control, and causing you to gain 2 life.
Repeat.
This elaborate planeswalker loop turns Teferi, Who Slows the Sunset and Elspeth, Sun's Champion into an unstoppable engine by using Ashnod's Altar to convert Elspeth's newly minted Soldier tokens into the mana required to fuel The Chain Veil's extra activation ability. With The Chain Veil untapping alongside other permanents every time Teferi uses his +1 ability, you can continuously cycle through their loyalty abilities to generate infinite mana, tokens, and lifegain.