Compare to offensive capabilities to Earthquake
At 0 Pillars both are useless
At 1 Pillar Earthquake is superior because Enlivening costs 1 more, and only creates a 1|1 (the creature is also a pillar)
At 2 Pillars Earthquake is still superior because Enlivening costs 1 more, and leaves a 2|2 plliar
At 3 Pillars Earthquake is still superior because Enlivening costs 1 more, and leaves a 3|3 plliar
At 4 Pillars Earthquake is still superior because Enlivening costs 1 more, and leaves a 4|4 (they both leave a pillar)
At 5 Pillars Earthquake has a 1 quanta advantage and doesn't create a 5|5 creature but Enlivening destroys 1 more pillar. Since a 5|5 Immortal is worth 7 quanta the question is 8 quanta or 1 pillar. (8.00 turns)
At 6 Pillars Earthquake has a 1 quanta advantage and doesn't create a 6|6 creature but Enlivening destroys 2 more pillars. Since a 6|6 Immortal is worth 9 quanta the question is 10 quanta or 2 pillars. (5.00 turns)
At 7 Pillars Earthquake has a 1 quanta advantage and doesn't create a 7|7 creature but Enlivening destroys 3 more pillars. Since a 7|7 Immortal is worth 10 quanta the question is 11 quanta or 3 pillars. (3.66 turns)
At 8 Pillars Earthquake has a 1 quanta advantage and doesn't create a 8|8 creature but Enlivening destroys 4 more pillars. Since a 8|8 Immortal is worth 12 quanta the question is 13 quanta or 4 pillars. (3.25 turns)
At 9 Pillars Earthquake has a 1 quanta advantage and doesn't create a 9|9 creature but Enlivening destroys 5 more pillars. Since a 9|9 Immortal is worth 13 quanta the question is 14 quanta or 5 pillars. (2.80 turns)
At 10 Pillars Earthquake has a 1 quanta advantage and doesn't create a 10|10 creature but Enlivening destroys 6 more pillars. Since a 10|10 Immortal is worth 15 quanta the question is 16 quanta or 6 pillars. (2.66 turns)
At X (X>10) Pillars Earthquake has a 1 quanta advantage and doesn't create a X|X creature but Enlivening destroys X-4 more pillars. Since a X|X Immortal is worth X+5 quanta the question is X+6 quanta or X-4 pillars. ([X+6]/[X-4] turns)
[X+6]/[X-4]=2 at 14 Pillars. So at 14 pillars Enlivening is superior to Earthquake if there are at least 2 (of your opponent's) turns remaining in the duel.
I believe that based on the above we can agree that offensively Enlivening is not superior to Earthquake until around 7-10 pillars. Since Earthquake is strictly better at 1-4 pillars and probably still better at 5-6 pillars, I think it is fair to say that Enlivening is balanced even when used offensively.
Defensive use
Unupped only considered. Upped would have quanta cost and benefit both reduced by 1
Pillars | Cost (including quanta not produced) | Benefit | Turns valued |
1 | 5 quanta and 1 pillar | 3 quanta and 1 pillar | 0 |
2 | 6 quanta and 2 pillars | 4 quanta and 1 pillar | 0 |
3 | 7 quanta and 3 pillars | 5 quanta and 1 pillar | 0 |
4 | 8 quanta and 4 pillars | 6 quanta and 1 pillar | 0 |
5 | 9 quanta and 5 pillars | 7 quanta and 1 pillar | 0 |
6 | 10 quanta and 6 pillars | 9 quanta and 1 pillar | 0 |
7 | 11 quanta and 7 pillars | 10 quanta and 1 pillar | 0 |
8 | 12 quanta and 8 pillars | 12 quanta and 1 pillar | 0 |
9 | 13 quanta and 9 pillars | 13 quanta and 1 pillar | 0 |
10 | 14 quanta and 10 pillars | 15 quanta and 1 pillar | 1 |
X (X>10) | X+4 quanta and X pillars | X+5 quanta and 1 pillar | 1 |
Unfortunately while hostile offensive use is balanced, defensive passive use is strictly foolish until 10 pillars and even then it is only valuable if that is the last turn. Please buff the Defensive passive use of this spell.
However there is one final use to consider. The last turn bomb. This would require you holding onto 1 Enlivening (extra would be useless) and using Enlivening with no intention of the opponent even getting a turn. This would be a very
like use of the card. In this case it does X damage for 4 quanta where X is the number of pillars. 2 Lightning bolts deal 10 damage and cost 4 quanta. Since Enlivening would only use 1 card (instead of 2 lightning bolts), Enlivening would be worth while as a bomb at 10 pillars or more.
All in all I would recommend either buffing the defensive use so it is worth while and thus give the card a
like use or to change it to
as a synergistic control/bomb in conjunction with Fire Bolt.
Sources: Quanta value of creatures (Mechanics of Creature Cost by PhantomFox
http://elementswiki.co.cc/articles/mechanics-of-creature-cost/)
Edited: Forgot to include the +2 quanta value for Immortality