Edison format ruling
Felgrand Dragon

Card effect (current official text)Cannot be Special Summoned except from the Graveyard, and only if it was sent there from the field. If this card is Special Summoned: Target 1 monster in your Graveyard; this card gains ATK equal to that monster's Level x 200.
Rulings
- The ATK gained by Felgrand Dragon when it is Special Summoned disappears when Felgrand Dragon is removed from the field or flipped face-down.
- If Skill Drain is face-up on the field when Felgrand Dragon is Special Summoned, or if Skill Drain is activated after Felgrand Dragon is Special Summoned, Skill Drain will negate Felgrand Dragon's ATK gaining effect. If Skill Drain is later negated or removed from the field, the ATK gain is not reapplied.
- When Felgrand Dragon is Special Summoned, its controller selects 1 monster in his/her GY as a target. If the selected monster is removed from play in chain to this effect, Felgrand Dragon's effect will disappear and it will not gain ATK.
- After Felgrand Dragon's ATK gaining effect is resolved, the ATK gain will not disappear if the selected monster is removed from the GY.
- The text "This monster cannot be Special Summoned except from the GY, and only if it was sent there from the field" is a condition and not an effect. It cannot be negated by "Dark Ruler Ha Des", etc.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Edison forum — sourced change requests get reviewed.