Primordial Sliver

Slivers you control have Sliver Evolve
(Whenever a sliver enters the battlefield under your control, if that sliver has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
When a sliver receives a +1/+1 counter from Sliver Evolve, you may put a 1/1 blue/green sliver creature token onto the battlefield tapped.