Leyline of the Elves

If Leyline of the Elves is in your opening hand,
you may begin the game with it on the battlefield.
Whenever an Elf creature enters the battlefield under your control, you may pay {1}{g}. If you do, chose one:
- put a +1/+1 counter on each elf you control.
- gain X life where X is equal to the number of elves you control.