Advanced format ruling
Cloudian - Nimbusman
Card effect (current official text)This card cannot be destroyed by battle. If this card is in face-up Defense Position, destroy it. You can Tribute any number of WATER monsters for the Tribute Summon of this card. When this card is Tribute Summoned, place 1 Fog Counter on it for each WATER monster you Tributed. This card gains 500 ATK for each Fog Counter on the field.
Current rulings for this card are maintained by Konami.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Advanced forum — sourced change requests get reviewed.