Shimmering Grotto

{T}: Add {C}.
{1}, {T}: Add one mana of any color.

Bonescythe Sliver

Sliver creatures you control have double strike. (They deal both first-strike and regular combat damage.)

Sliver creatures you control have flying.

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

Sliver creatures you control have first strike. (They deal combat damage before creatures without first strike.)

Sliver creatures you control have vigilance. (Attacking doesn't cause them to tap.)