At the beginning of combat on your turn, target creature you control gets +1/+0 and gains haste until end of turn.

Daybound (If a player casts no spells during their own turn, it becomes night next turn.)

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Storm-Charged Slasher

At the beginning of combat on your turn, target creature you control gets +2/+0 and gains trample and haste until end of turn.

Nightbound (If a player casts at least two spells during their own turn, it becomes day next turn.)