Wall Crawl

When this enchantment enters, create a 2/1 green Spider creature token with reach, then you gain 1 life for each Spider you control.
Spiders you control get +1/+1 and can't be blocked by creatures with defender.

Mountain

Radioactive Spider

Reach, deathtouch
Fateful Bite — {2}, Sacrifice this creature: Search your library for a Spider Hero card, reveal it, put it into your hand, then shuffle. Activate only as a sorcery.

Scarlet Spider, Ben Reilly

Web-slinging {R}{G} (You may cast this spell for {R}{G} if you also return a tapped creature you control to its owner's hand.)
Trample
Sensational Save — If Scarlet Spider was cast using web-slinging, he enters with X +1/+1 counters on him, where X is the mana value of the returned creature.

Spider-Punk

Riot (This creature enters with your choice of a +1/+1 counter or haste.)
Other Spiders you control have riot.
Spells and abilities can't be countered.
Damage can't be prevented.

Rhino's Rampage

Target creature you control gets +1/+0 until end of turn. It fights target creature an opponent controls. When excess damage is dealt to the creature an opponent controls this way, destroy up to one target noncreature artifact with mana value 3 or less.

Spider-Ham, Peter Porker

When Spider-Ham enters, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")
Animal May-Ham — Other Spiders, Boars, Bats, Bears, Birds, Cats, Dogs, Frogs, Jackals, Lizards, Mice, Otters, Rabbits, Raccoons, Rats, Squirrels, Turtles, and Wolves you control get +1/+1.

Twitching Doll

{T}: Add one mana of any color. Put a nest counter on this creature.
{T}, Sacrifice this creature: Create a 2/2 green Spider creature token with reach for each counter on this creature. Activate only as a sorcery.

Roaming Throne

Ward {2}
As this creature enters, choose a creature type.
This creature is the chosen type in addition to its other types.
If a triggered ability of another creature you control of the chosen type triggers, it triggers an additional time.

Spinneret and Spiderling

Whenever you attack with two or more Spiders, put a +1/+1 counter on Spinneret and Spiderling.
Whenever Spinneret and Spiderling deals 4 or more damage, exile the top card of your library. Until the end of your next turn, you may play that card.

Taurean Mauler

Changeling (This card is every creature type.)
Whenever an opponent casts a spell, you may put a +1/+1 counter on this creature.