Arachnoform

Enchant creature
Enchanted creature gets +2/+2, has reach, and is every creature type.

Cloudshredder Sliver

Sliver creatures you control have flying and haste.

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

Sliver creatures you control have menace. (They can't be blocked except by two or more creatures.)

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

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

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

This land enters tapped unless a player has 13 or less life.
{T}: Add {G} or {W}.

This land enters tapped. As it enters, choose a color other than red.
{T}: Add {R} or one mana of the chosen color.

This land enters tapped unless a player has 13 or less life.
{T}: Add {R} or {W}.

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

This land enters tapped. As it enters, choose a color other than white.
{T}: Add {W} or one mana of the chosen color.

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