When you cast this spell, each player reveals the top card of their library. Naya Soulbeast enters the battlefield with X +1/+1 counters on it, where X is the total mana value of all cards revealed this way.
Trample
Naya Soulbeast’s last ability triggers while Naya Soulbeast is on the stack. After that ability resolves, players will be able to cast spells and activate abilities knowing how many counters Naya Soulbeast will enter the battlefield with if it resolves.