Twisted Cosmo

Cosmo is easy to read, which is why the interesting part is the company he keeps. On his own the wiki lists no mechanic, only the standard Common profile: walk 10, chase 18 (tied for 15th of 37, the median), vision of 26 in a circle and 60 direct, hearing to 125 and an attention span of 1.5 seconds. The twist is Twisted Sprout. If Sprout is on the same floor, he follows Cosmo around, and Sprout is a Main that leaves deadly tendrils under any Toon it detects.

So a floor with both is more dangerous than either number suggests. Treat Cosmo as a signal: if you see him wandering with a plant trailing behind, expect tendrils nearby and give that area a wide berth, since Sprout sees 28 in a circle and 60 direct and hears 150. Cosmo's own Toon has 4 stars of Stealth and 4 of Stamina, enough to slip away and then recover, though only 1 star of Skill Check, so the Toon heals by giving up one of its own hearts to a teammate.

Cosmo is a Common Twisted. 100% Research unlocks the Sweet Charm trinket, which reduces active ability cooldown by 8%.