Veldri, Strange Devastator enters the battlefield with X +1/+1 counters and X head counters.

When you tap a source you control for mana, add {X} to your mana pool where X is the number of head counters on Veldri, Strange Devastator. Spend this mana only to cast spells with {X} in its mana cost.

For each time Veldri, Strange Devastator has been cast from the command zone, pay {X} instead of {2}.