Helga, Skittish Seer
Legendary Creature — Frog Druid
Whenever you cast a creature spell with mana value 4 or greater, you draw a card, gain 1 life, and put a +1/+1 counter on Helga.
: Add X mana of any one color, where X is Helga's power. Spend this mana only to cast creature spells with mana value 4 or greater or creature spells with 
in their mana costs.
David Petersen
Bloomburrow (BLB)
• #332Rulings
If you spend the mana added by Helga's last ability on a creature spell with {X} in its mana cost, the mana can be spent on any part of that spell's total cost. You're not limited to spending it only on the {X} part.
(wotc • 2024-07-26)
Helga's last ability is a mana ability. It doesn't use the stack and can't be responded to.
(wotc • 2024-07-26)
If a spell has {X} in its mana cost, use the value chosen for that X to determine the mana value of that spell.
(wotc • 2024-07-26)
You don't have to spend all the mana added by Helga's last ability on the same spell.
(wotc • 2024-07-26)
Rulings
If you spend the mana added by Helga's last ability on a creature spell with {X} in its mana cost, the mana can be spent on any part of that spell's total cost. You're not limited to spending it only on the {X} part.
(wotc • 2024-07-26)
Helga's last ability is a mana ability. It doesn't use the stack and can't be responded to.
(wotc • 2024-07-26)
If a spell has {X} in its mana cost, use the value chosen for that X to determine the mana value of that spell.
(wotc • 2024-07-26)
You don't have to spend all the mana added by Helga's last ability on the same spell.
(wotc • 2024-07-26)