Codex: Chaos Space Marines (1999), p21 — Chaos Space Marine Vehicle Upgrades & Gifts

Nurgling Infestation: The vehicle has been infected by Nurgle's Rot and is infested with pestilence - decaying limbs and tentacles begin to grow from it. The vehicle is rotten to the core, slimy ooze covers the tank and Nurglings swarm all over it. The armour value of each of the vehicle's locations is increased by +1 point, up to a maximum of 14 points.