This strategy requires some form of speed enhancement to really work well. On smaller battle fields it should work well without speed enhancement. It will work to some degree on any map without speed, but not as well.
Also it's only viable for enemy armies that are mostly flightless with fewer action points.
If no speed boosting items have been discovered, these two options are reliably available:
Mana Accelerator used every round it will help to cast a Phantom every round as well. But will use up a Rage Skill casting.
Haste spell will use up a precious spell round. However Haste III only costs 10 mana and gives your entire army +2 speed for 4 rounds. With Mage class higher magic, Haste III + Phantom can be done in round 1.
Speed boosting items (if discovered) will save you spells and rage skills for other uses:
Belt of the Victor (artifact) provides +1 speed to all units but is a very hard to find composite item included in the gift bag. (special mod needs to be installed)
Skates (boots) provide +1 speed to all pedestrians on snow terrain. (gift bag mod)
Boots of the Pilgrim (boots) provide +1 speed to the slowest troop
Ogre Sandals (boots) provide +1 speed to Ogres, Giants & Trolls
The Ogre set is excellent for this strategy and Giants in general.
--- Ogre Set ---
+2500 Leadership (allows 1 more Giant and helps for the next one)
Ogre's Club (weapon) (finding 2 of these is really nice for the 40% damage increase)
+4 Attack
+20% Damage for Ogre's, Troll's & Giant's
Ogre Sandals (boots)
+2 Defense
+1 Speed of Ogre's, Troll's & Giant's (this is the real sweet deal, lucky if you find 2)
Ogre's Belt (belt)
+4 Defense (many better items can fill this slot, but with the set +4 def. is pretty good)
--- end Ogre Set ---
Other items of special benefit to Giants:
Horn of King Borg (artifact)
+5 Attack to all Dwarfs
–10% Leadership requirement for all dwarfs (includes Giants)
–1 Initiatives to your humans and elves
Fighting Pole-axe (weapon) (sorry don't know the actual in game name)
+20% Damage for fighters with melee weapons
Drill (weapon) (always found after defeating the Driller boss)
+25 Physical damage
-1 Initiative
Only affects fighters with melee weapons
Army Composition:
The idea being the mages all have pretty good range attack. Arch-Mage can Magic Shield the main Giant stack. Demonologist, Druid & Royal Griffin all summon free support units. RG is a fast and powerful tank unit.
Several good substitutions might be: Shaman for totem of life to bring defense and healing to the invading Giants + Dancing Axes for healing and offensive strike. Hunters for strong range attack. Trolls for super tank, especially if holding the Ogre set items. Dragons for fast powerful tanks.
The Power of Phantom Giants Strategy
(1) First activate running for Giants, move Giants towards enemy army but don't use the last action point.
(2) Cast Phantom on the Giants and place the phantom Giants 1 space in front of the real Giants so they start as close to the enemy army as possible.
(3) Instruct real Giants to do Earthquake.
(4) Activate running for phantom Giants, move giants toward enemy army, but save the last action point.
(5) Instruct phantom Giants to use Earthquake for their last action point.
If there aren't too many obstacles on the field it's possible to have the phantom Giants in the midst of the enemy army for the 1st Earthquake in the 1st round. If you keep your real army back the enemy army will most likely target the phantom Giants, saving your real army and giving you more rounds to wear them down.
(in this photo the enemy is weak so I'm just charging)
(5)At this point it's possible to continue to Phantom the real Giant stack and flood the enemy army with Giant tanks and Earthquakes.
Use Mana Accelerator to maintain mana.
Look at that angry Polar Bear, he doesn't like earthquakes!
In this scene all enemies are attacking the phantom Giants and ignoring the real army which is a bit further back.
The Phantom Giants work really well in this battle against all Hyenas.
Granted this is a very easy battle and almost anything would work well.
Here is a scenario using Mana Accelerator to get the real big Giant stack as close to the enemy as possible before 1st Earthquake.
Giants use run and move into place saving 1 action point. Phantom is carefully placed first. Mana Accelerator is carefully placed 2nd.
Real large Giant stack grabs Mana Accelerator gaining 2 action points (this is later stage MA upgrade, early has 1 action point). Moves 1 more space toward the enemy lines (having gained a total of 2 move spaces plus 1 extra action point remaining). Main large stack uses Earthquake with impressive results.
Hyenas make their move. Luckily most went for the Executioner, the others just ran up to the real Giant stack and did nothing, some attacked the phantom Giants. Now phantom Giants Earthquake.
3rd phantom Giants are made. So far the Giants and phantoms have done most of the work. Ideally I should have had Arch-Mages (Magic Shield) and other mage/range units supporting them. The Dragons and Troll did nothing the whole match but move around or defend.
