Triggered abilities you control can't cause you to sacrifice or exile creature tokens you control
The exact combo lines can be modular, but the core idea stays the same: get Lumra onto the battlefield, kill Lumra and/or sacrifice your Lands with the ETB on the stack, bring everything back, generate more resources than you spent, and repeat
recommended retail prices for these are $16.99 in the US ($21.99 in Canada)
And flavor wise, the Slivers are about evolution, and will often grow extra physical aspects like Two-Headed Sliver or Plated Sliver, so changing their base form is in line with who they are
Some people want to watch the world burn, but others just want to watch nothing happen #4: Stoneforge Mystic Stoneforge Mystic, on the other hand, now that is a reliable way to make things happen