Grist, Voracious Larva

A transforming double-faced card enters the battlefield with its front face up by default, unless a spell or ability instructs you to put it onto the battlefield transformed or allows you to cast it transformed, in which case it enters with its back face up.

Each face of a transforming double-faced card has its own set of characteristics: name, types, subtypes, abilities, and so on. While a transforming double-faced permanent is on the battlefield, consider only the characteristics of the face that's currently up. The other set of characteristics is ignored.

Each transforming double-faced card in this set is cast with its front face up. In every zone other than the battlefield, consider only the characteristics of its front face. If it is on the battlefield, consider only the characteristics of the face that's up; the other face's characteristics are ignored.

Except for the listed exceptions, the tokens created by Grist, the Plague Swarm's last ability copy exactly what was printed on the original cards and nothing else. They don't copy any information about the objects those cards were before they were put into your graveyard.

If Grist, Voracious Larva leaves the battlefield while its triggered ability is on the stack, you can't exile it from the zone it's put into, so you won't return it to the battlefield transformed under its owner's control.

If a card copied by one of the tokens had any "when [this creature] enters the battlefield" abilities, the appropriate token also has those abilities and will trigger them when it's created. Similarly, any "as [this creature] enters the battlefield" or "[this creature] enters the battlefield with" abilities that a token has copied will also work.

If any of the copied cards have {X} in their mana costs, {X} is 0.

If you are instructed to put a card that isn't a double-faced card onto the battlefield transformed, it will not enter the battlefield at all. In that case, it stays in the zone it was previously in. For example, if a single-faced card is a copy of Ral, Monsoon Mage, choosing to exile that permanent during the resolution of its triggered ability will cause it to remain in exile.

In some rare cases, a spell or ability may cause Grist, Voracious Larva to transform while it's a creature (front face up) on the battlefield. If this happens, Grist, the Plague Swarm won't have any loyalty counters on it and will subsequently be put into its owner's graveyard.

In the Commander variant, a double-faced card's color identity is determined by the mana costs and mana symbols in the rules text of both faces combined. If either face has a color indicator or basic land type, those are also considered. For example, Ral, Monsoon Mage's color identity is blue and red, since its front face is red and its back face has a blue and red color indicator.

The back face of a transforming double-faced card usually has a color indicator that defines its color. Colorless back faces, such as lands, do not.

The mana value of a transforming double-faced card is the mana value of its front face, no matter which face is up.

The tokens are Insects instead of their other creature types, and they're black and green instead of their other colors. These are copiable values of the tokens that other effects may copy.

You can activate one of Grist, the Plague Swarm's loyalty abilities the turn it enters the battlefield. However, you may do so only during one of your main phases when the stack is empty. For example, if Grist, the Plague Swarm enters the battlefield during combat, there will be an opportunity for your opponent to remove it before you can activate one of its abilities.