REDU format ruling
Power Supplier

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)Once per turn, you can select 1 face-up monster you control. It gains 400 ATK while you control this face-up card. (A monster cannot gain more than 400 ATK from this card's effect.)
Rulings
- This effect continuously targets each monster you select for as long as "Power Supplier" is face-up on the field.
- You cannot apply "Power Supplier’s" effect on the same monster targeted during the previous turn.
- If a monster targeted by "Power Supplier" is affected by "Shrink" or "Megamorph" you recalculate the original ATK of the monster and then reapply the +400 ATK from "Power Supplier.
- If "Skill Drain" is activated, monsters targeted by "Power Supplier" lose the +400 ATK. If "Skill Drain" is removed from the field, the effect of "Power Supplier" is reapplied and the targeted monsters will regain the +400 ATK.
- If your opponent gains control of one of your monsters that was targeted by "Power Supplier" it will still gain the ATK.
- If you target a different monster each turn, all the previously targeted monsters’ ATK remain increased.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.