Undergrowth — When this creature enters, target creature gains menace and gets +X/+0 until end of turn, where X is the number of creature cards in your graveyard. (It can't be blocked except by two or more creatures.)
The value of X is determined only as the undergrowth ability resolves. If the number of creature cards in your graveyard changes later in the turn, the target creature is unaffected.
2018-10-05 • wotc
If there are no creature cards in your graveyard, the target creature just gains menace until end of turn.
2018-10-05 • wotc
Creature cards with other types, such as artifact creature cards, count for undergrowth abilities.
2018-10-05 • wotc
Because tokens aren't cards, they never count for undergrowth abilities.