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From my ideas:
Vampire Amulet (presumably, major)
At the start of the battle, a random friendly unit receives the "Vampirism" spell for 10 turns, allowing it to convert up to 50% of the damage dealt into health (i.e., like the vampires' ability). If the army contains both ranged and melee units, Vampirism cannot be applied to ranged units. If there are only ranged units, it is applied to a random one. The spell is cast in the usual way and can be dispelled. All vampires in the hero's army receive +2 to attack and defense.
Goblin Shaman's Rattle (left hand, presumably, major)
Gives the hero an active, non-magical ability called "Magic Corruption," which works on the same principle as the Goblin Shaman's ability, consumes only 50% of the hero's initiative, does not require mana, and lasts until the first cast of a targeted spell/enemy hero. The strength of the casting hero is determined by the same formula as the strength of the enemy hero. All goblins in the hero's army receive +1 to morale.
*** (name in development, helmet, relic)
All friendly units in defense receive the "Unending Retaliation" ability. (If the hero has the "Readiness" skill, units do not receive "Unending Retaliation" when given the "Defense" order, but instead receive an additional +5 to defense. Units that already have the "Unending Retaliation" ability built-in also receive +5 to defense.)
Sword of Fury (presumably, major)
If a friendly unit attacks, it receives +3 to attack. If it defends or waits, it receives -3 to attack. For the next similar action, it receives an additional +/- 2 to attack, and for the 3rd and subsequent actions, +/- 1. If the sequence of identical actions (attack/defense or wait) is broken, the unit loses all bonuses and penalties to attack, and everything starts over. Movement without attacking does not affect the increase/decrease in attack. Orcs lose twice as much attack when waiting, and dwarves do not lose attack when defending, and any accumulated attack bonuses are not reset.
Banner of the Dreadful Leader (presumably, major, not sure where it would fit best)
The hero forces the units to fight much more effectively, but under the threat of their own death, and as the chances of victory decrease, the units' morale drops, and eventually, they may betray the hero.
Units receive +5 to attack and +1 to initiative. At the same time, they also receive some penalties:
75-100% of the units in the squad (from the number that was at the beginning of the battle): -1 to morale.
50-74% of the units in the squad: -2 to morale.
30-50% of the units in the squad: -3 to morale.
Less than 30%: units of level 1-3 inclusive - betrayal (like goblins, they switch to the enemy's side). Level 4 and 5 -5 to morale, level 6 and 7 -3 to morale.
Undead units are immune to any effect of the artifact.