Invigorate

Mana cost: {2}{G}
Type: Instant
Set: Masters 25 #173 (uncommon)
Price: $0.37 USD

If you control a Forest, rather than pay this spell's mana cost, you may have an opponent gain 3 life.
Target creature gets +4/+4 until end of turn.

Invigorate has 14 printings, first in Mercadian Masques (1999). EDHREC ranks it #3,509 among Commander cards. It appears most in Kotis, the Fangkeeper decks (6,390 on EDHREC). 1 public deck on TCG runs it. It has 2 official rulings.

Legality

commander: legal
legacy: legal
vintage: legal
pauper: banned
modern: not legal
pioneer: not legal
standard: not legal
brawl: not legal

Public decks that run Invigorate

Mirror Mastery - Commander 2011, led by Riku of Two Reflections

Commanders that run Invigorate most

Deck counts from EDHREC.

Kotis, the Fangkeeper: 6,390 decks
Tifa Lockhart: 5,202 decks
Xyris, the Writhing Storm: 4,546 decks
Shroofus Sproutsire: 4,192 decks
Sergeant John Benton: 4,021 decks
Selvala, Heart of the Wilds: 1,982 decks
The Howling Abomination: 1,932 decks
Marwyn, the Nurturer: 1,829 decks

Often played with Invigorate

Cards that show up in the same decks on EDHREC.

Rulings

2020-08-07: To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as the alternative cost of Invigorate), add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.
2020-08-07: If an effect says that an opponent can't gain life, you can't have that player gain life to pay Invigorate's alternative cost. If an effect instead replaces life gain, such as that of Sulfuric Vortex, you may choose to pay the cost even though the cost's action is replaced with nothing.