Reflex Sliver

Brood Sliver

Whenever a Sliver deals combat damage to a player, its controller may create a 1/1 colorless Sliver creature token.

Sliver creatures you control have "Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."

All Sliver creatures have "Whenever this creature is dealt damage, put a +1/+1 counter on it." (It must survive the damage to get the counter.)

Flash
Any player may cast Sliver spells as though they had flash.

Thriving Grove enters tapped. As it enters, choose a color other than green.
{T}: Add {G} or one mana of the chosen color.

All Slivers have "{T}: Add one mana of any color."

Sliver creatures you control have "{T}: Add one mana of any color."

Sliver creatures you control have trample. (A creature with trample can deal excess combat damage to the player or planeswalker it's attacking.)

Sliver creatures you control have deathtouch. (Any amount of damage a creature with deathtouch deals to a creature is enough to destroy it.)