Creatures can't attack you or a planeswalker you control unless their controller pays {1} for each of those creatures beyond the first.

Vigilance
When Hardlight Paragon enters, distribute two +1/+1 counters among one or two target creatures.

Vigilance
Whenever another creature entering the battlefield under your control causes an ability of a permanent you control to trigger, put a +1/+1 counter on that creature and you gain 1 life. This ability triggers only once each turn.

Flying
When Hoarding Rocs enters, look at the top three cards of your library. You may reveal an artifact card from among them and put it into your hand. Put the rest on the bottom in a random order.

Favored
Whenever Iara, Blessed-Hart attacks, Iara and another target attacking creature gain double strike until end of turn.

Flash
When Lauded Orator enters, target creature gets +0/+2 until end of turn.

Whenever Lithe Stalker or another artifact you control enters, artifact creatures you control gain first strike until end of turn.

New Recruit has first strike as long as it is attacking.
When New Recruit dies, create a 2/2 black Zombie creature token.

Lifelink
Whenever you gain life, noncreature spells your opponents cast cost {1} more to cast until your next turn. This ability triggers only once each turn.

Flying
When Powerline Warbler enters, return target artifact card from your graveyard to your hand.

Approval — When Prismatic Propagandist enters, create X 1/1 colorless Soldier creature tokens, where X is the number of colors among permanents you control.

{VP}{VP}{VP}: Pristine Star gains double strike until end of turn.

Flying
Whenever an opponent spends mana, if it wasn't spent to cast a spell from their hand, you draw a card. This ability triggers only once each turn.

When Synod of Sanctions enters, exile up to one target creature. For as long as that card remains exiled, its owner may cast it. A spell cast this way costs {1} more to cast.

Lifelink
When Traxian General enters, create a 0/0 white Army creature token. Put a +1/+1 counter on each Army you control.

Whenever Twilight Vagabond attacks, put a +1/+1 counter on it.
Cybersoul {2}{W}

First strike, vigilance
Whenever Unburnt Maiden enters or attacks, you may have it dare X, where X is the number of creatures you control. If you don't, create a 1/1 white Warrior creature token.

Flying
When Whipwing Dragonfly enters, you gain 2 life.

Flying
When Civic Copterist enters, teach target creature flying.

Flying, ward {1}
Whenever you cast an instant or sorcery spell, mill a card. Return an instant or sorcery card milled this way to your hand. If you can't, put a +1/+1 counter on Covetous Frostwyrm.

Approval — When Dampening Reconciliator enters, tap up to one target creature and put X stun counters on it, where X is the number of colors among permanents you control.

When Disguising Barber enters, you may have another target creature you control become a copy of any creature on the battlefield for as long as you control Disguising Barber.

Favored
Whenever your Champion attacks, it can't be blocked this turn.

Decayed
{2}{U}, Exile Expendable Researcher from your graveyard: Return target instant or sorcery card from your graveyard to your hand. Activate only as a sorcery.

Flying
Whenever an artifact without a loop counter on it is put into your graveyard from the battlefield, return it to the battlefield with a loop counter on it.
{2}{U}: Remove a loop counter from target artifact.