Principle is a Runeword "RalGulEld" in Diablo 2 Resurrected (D2R). It requires these 3 runes to be inserted into a socketed item in the exact order: Ral + Gul + Eld . The eligible bases for Principle are the following: Body Armors . This is the only Runeword in the game that has X% Chance to cast Level X Holy Bolt on striking attribute.
PrinciplePrincipleScarab Husk
Ral · Gul · Eld
Defense: 369 - 474
Durability: 28 of 28
Required Strength: 95
Required Level: 53
100% Chance to cast Level 5 Holy Bolt on striking
+2 to Paladin Skill Levels
+50% Damage to Undead
+(100 - 150) to Life
15% Slower Stamina Drain
+5% to Maximum Poison Resist
Fire Resist +30%
Socketed (3)
Trade items on d2trader.net

How to obtain Principle

The fastest way to get this item on Battle.net is via trading, you can use the Item Price Checker to see how much Principle is worth.
Another way of getting this Runeword is by farming the runes and the base. Find the drop rates of these items in the Item Database.

Principle bases

The best base for Principle is Scarab Husk. Below is a list of all eligible 3 socket bases for Principle.