Generator Servant
Creature — Elemental
, Sacrifice this creature: Add 
. If that mana is spent on a creature spell, it gains haste until end of turn. (That creature can attack and as soon as it comes under your control.)
Mathias Kollros
The List (PLST)
• #M15-143Rulings
An instant or sorcery spell is not a creature spell, even if that spell creates creature tokens.
(wotc • 2018-12-07)
If the mana is spent on two different creature spells, each of those spells (and resulting creatures) will gain haste until end of turn.
(wotc • 2018-12-07)
If the mana is spent on a noncreature spell that becomes a creature later in the turn, that creature won't have haste.
(wotc • 2018-12-07)
If a creature spell has generic mana only in its alternative or additional cost, the creature will still gain haste.
(wotc • 2018-12-07)
Rulings
An instant or sorcery spell is not a creature spell, even if that spell creates creature tokens.
(wotc • 2018-12-07)
If the mana is spent on two different creature spells, each of those spells (and resulting creatures) will gain haste until end of turn.
(wotc • 2018-12-07)
If the mana is spent on a noncreature spell that becomes a creature later in the turn, that creature won't have haste.
(wotc • 2018-12-07)
If a creature spell has generic mana only in its alternative or additional cost, the creature will still gain haste.
(wotc • 2018-12-07)