Aunt May

Whenever another creature you control enters, you gain 1 life. If it's a Spider, put a +1/+1 counter on it.

Plains

{1}, {T}, Sacrifice this artifact: Target creature you control explores. Activate only as a sorcery. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on that creature, then put the card back or put it into your graveyard.)

Spider-Woman, Stunning Savior

Flying
Venom Blast — Artifacts and creatures your opponents control enter tapped.

Unstable Experiment

Target player draws a card, then up to one target creature you control connives. (Draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on that creature.)

University Campus

This land enters tapped.
{T}: Add {W} or {U}.
{4}, {T}: Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Restless Anchorage

This land enters tapped.
{T}: Add {W} or {U}.
{1}{W}{U}: Until end of turn, this land becomes a 2/3 white and blue Bird creature with flying. It's still a land.
Whenever this land attacks, create a Map token.

SP//dr, Piloted by Peni

Vigilance
When SP//dr enters, put a +1/+1 counter on target creature.
Whenever a modified creature you control deals combat damage to a player, draw a card. (Equipment, Auras you control, and counters are modifications.)

Sheltered by Ghosts

Enchant creature you control
When this Aura enters, exile target nonland permanent an opponent controls until this Aura leaves the battlefield.
Enchanted creature gets +1/+0 and has lifelink and ward {2}.

Island

With Great Power...

Enchant creature you control
Enchanted creature gets +2/+2 for each Aura and Equipment attached to it.
All damage that would be dealt to you is dealt to enchanted creature instead.

Spider-Byte, Web Warden

When Spider-Byte enters, return up to one target nonland permanent to its owner's hand.

Sun-Spider, Nimble Webber

During your turn, Sun-Spider has flying.
When Sun-Spider enters, search your library for an Aura or Equipment card, reveal it, put it into your hand, then shuffle.

Skyward Spider

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
This creature has flying as long as it's modified. (Equipment, Auras you control, and counters are modifications.)

Spider-Man No More

Enchant creature
Enchanted creature is a Citizen with base power and toughness 1/1. It has defender and loses all other abilities. (It also loses all other creature types.)

Floodfarm Verge

{T}: Add {W}.
{T}: Add {U}. Activate only if you control a Plains or an Island.

Shardmage's Rescue

Flash
Enchant creature you control
As long as this Aura entered this turn, enchanted creature has hexproof.
Enchanted creature gets +1/+1.