While a measly 10 damage doesnt seem like a lot, it can be invaluable for this deck against specific cards
The reason I think of this as a puzzle then, is that now we want creatures that when added to Putrefax or Skitters become lethal but arent blobs that sit in our hand uselessly when we draw them
Artifacts Want to drop this early, then use it for many repeatable tutors to potentially win the game right there, or to grab synergetic elements to overrun the game

Mewtwo Collection Battle Arena Decks: Mewtwo EX vs Darkrai EX Elite Trainer Box [Mewtwo X] Elite Trainer Box [Mewtwo Y] $990.00 BREAKthrough Pin Blisters [Mega Mewtwo] (Set of 2) BREAKthrough Three Pack Pin Blisters [Mega Mewtwo X] BREAKthrough Three Pack Pin Blisters [Mega Mewtwo Y] Mega Mewtwo Collection (Set of 2) Armored Mewtwo - SM228 #SM228Promo $292.99 Cresselia - 87/236 (Mewtwo Stamped) #87Promo $0.24 Cynthia - 119/156 (Mewtwo Stamped) #119Promo $0.33 Eevee - 49/68 (Mewtwo Stamped) #49Promo $0.82 Espeon - 89/214 (Mewtwo Stamped) #89Promo $1.51 Hau - 120/149 (Mewtwo Stamped) #120Promo $0.15 M Mewtwo EX #43None $49.75 M Mewtwo ex - 028/059 #28Double Rare $80.00 Pikachu (27) #27Common $0.28 Ditto #53Holo Rare $5.48 Slaking V #58Ultra Rare $0.68 Articuno #24Holo Rare $0.40 Mewtwo VSTAR #31Ultra Rare $7.14 Slowbro #20Uncommon $0.19 Ivysaur #2Uncommon $0.24 Bulbasaur #1Common $0.25 Xatu #33Uncommon $0.12 Alolan Exeggutor V #5Ultra Rare $0.88

We can Gush for free from the top to break the pile, or just Finale of Devastation X=2 for Thoracle, leaving 3 cards left exactly (Glarb can surveil 2 more if we need to)
Essentially, it was a threshold that triggers once an opponent has gained three or more poison counters - meaning there was value in just a smidgen of poison, as well as a lethal dose