Scaling Type:
Linear scaling (additive) for thorns (+2 per 1% armor per copy) and armor (+10% raw per copy)
Note: Armor uses hyperbolic scaling
Detailed Explanation
Gain +2 Thorns for every 1% Armor . Also gains 10% Armor.
Note that Armor is a stat that uses hyperbolic scaling. This means that although spiky shield does give you "+10% armor" this is the raw input number, and is calculated through a hyperbolic scaling formula before applied to how much armor you actually gain.
Note that Armor is a stat that uses hyperbolic scaling. This means that although spiky shield does give you "+10% armor" this is the raw input number, and is calculated through a hyperbolic scaling formula before applied to how much armor you actually gain.
How it Stacks
You gain a "raw" +10% armor for each copy (before calculated through the hyperbolic scaling formula)
The amount of thorns also scales linearly with the amount of spiky shields you have
The amount of thorns also scales linearly with the amount of spiky shields you have
$$
\text{Thorns} = 2 \cdot \text{amount} \cdot (\text{Armor}\%)
$$