Neyith of the Dire Hunt
Legendary Creature — Human Warrior
Whenever one or more creatures you control fight or become blocked, draw a card.
At the beginning of combat on your turn, you may pay 
. If you do, double target creature's power until end of turn. That creature must be blocked this combat if able. ( can be paid with either 
or .)
Magali Villeneuve
Jumpstart (JMP)
• #30Rulings
If each creature the defending player controls can’t block for any reason (such as being tapped), then the target creature isn’t blocked. If there’s a cost associated with blocking the target creature, the defending player isn’t forced to pay that cost, so it doesn’t have to be blocked in that case either.
(wotc • 2020-06-23)
A creature “fights” when an effect instructs it to fight. Dealing combat damage isn’t fighting.
(wotc • 2020-06-23)
The defending player, not you, chooses which creature blocks the target creature.
(wotc • 2020-06-23)
You draw just one card as Neyith’s first ability resolves, no matter how many creatures you control fought or became blocked.
(wotc • 2020-06-23)
If an effect instructs you to “double” a creature’s power, that creature gets +X/+0, where X is its power as that effect begins to apply. If its power is negative, instead it gets -X/-0 where X is how far below 0 its power is. The value of X won’t change if another effect alters the creature’s power later in the turn.
(wotc • 2020-06-23)
While resolving Neyith’s last ability, you can’t pay multiple times to double a creature’s power more than once or to double more than one creature’s power.
(wotc • 2020-06-23)
If the target creature has menace, two creatures must block it if able.
(wotc • 2020-06-23)
Only one creature is required to block the target creature. Other creatures may also block it and are free to block other creatures or not block at all.
(wotc • 2020-06-23)
Rulings
If each creature the defending player controls can’t block for any reason (such as being tapped), then the target creature isn’t blocked. If there’s a cost associated with blocking the target creature, the defending player isn’t forced to pay that cost, so it doesn’t have to be blocked in that case either.
(wotc • 2020-06-23)
A creature “fights” when an effect instructs it to fight. Dealing combat damage isn’t fighting.
(wotc • 2020-06-23)
The defending player, not you, chooses which creature blocks the target creature.
(wotc • 2020-06-23)
You draw just one card as Neyith’s first ability resolves, no matter how many creatures you control fought or became blocked.
(wotc • 2020-06-23)
If an effect instructs you to “double” a creature’s power, that creature gets +X/+0, where X is its power as that effect begins to apply. If its power is negative, instead it gets -X/-0 where X is how far below 0 its power is. The value of X won’t change if another effect alters the creature’s power later in the turn.
(wotc • 2020-06-23)
While resolving Neyith’s last ability, you can’t pay multiple times to double a creature’s power more than once or to double more than one creature’s power.
(wotc • 2020-06-23)
If the target creature has menace, two creatures must block it if able.
(wotc • 2020-06-23)
Only one creature is required to block the target creature. Other creatures may also block it and are free to block other creatures or not block at all.
(wotc • 2020-06-23)