A curious beast that looks like a tuft of grass and can spontaneously duplicate itself. Grasslings appear to multiply themselves after gaining enough energy from eating;

When a mouth emerges from this strange creature, it begins to happily munch on the black ash. Satiated, it shivers violently and within a few seconds, a second ball pops out of the first. It too reveals a mouth and begins to feast on the ashes. Within a very short amount of time, there are over a dozen of these ash-eating grasslings covering the arena. - Tome of Encounters (RPA-SQ1)

A rift opens and a lump of grass about the size of a small dog rolls into the arena. When a mouth emerges from this strange creature, it begins to happily munch on the black ash. Satiated, it shivers violently and within a few seconds, a second ball pops out of the first. - Tome of Encounters (RPA-SQ1)

The Colosseum of Ashes has a special solution for exterminating the Grasslings;

A huge force of arena guards pours out of the northern gate, spraying the grasslings with a gray liquid that dissolves them on contact. - Tome of Encounters (RPA-SQ1)

A Grassling jumps through a rift to the Colosseum of Ashes and quickly grows its numbers. - Tome of Encounters (RPA-Tome-SQ1-51)

It’s not hard to see where this is going. Harmless as any one of these creatures may be, they could soon number in the thousands. Your only hope is to act quickly. - Tome of Encounters (RPA-Tome-SQ1-52)

• Choose brute force in dealing with the growing threat:
  • Slay them all and the green that fills the ash eventually turns to black.
  • They quickly become too much for you to handle are dealt with by the guards.
• Try to bring them back to where they came from:
  • Corral them into the rift without any of their lives being lost.
  • They quickly become too much for you to handle are dealt with by the guards.

After the incident, you adopt a tiny straggler;

You wait for a moment for a new ball of grass to spawn from the one you hold in your hands. When none does, you decide it is safe to keep the creature as a pet. As long as it does not begin to rapidly multiply, it seems harmless enough. What’s the worst that could happen? - Tome of Encounters (RPA-Tome-SQ1-56)