GoblinHealth: 5Attack: 4Shots: noneMovement: ground
40 gold (15)Hex size: 1Defence: 2Dmg: 1-2Spd: 5 (slow)
Slightly weaker than average for level 1, but better than imp for a smaller price. Highly populated, goblin is a good offensive unit to start with. Nice speed for level 1, especially after the upgrade. Defence is lower than attack, so be sure to attack before attacked.
HobgoblinHealth: 5Attack: 5Shots: noneMovement: ground
50 gold (15)Hex size: 1Defence: 3Dmg: 1-2Spd: 7 (extra swift)
The speed is worth 10 gold, combined attack and defence increase. Hobgoblins are more able to attack before failing to defend themselves. However, the damage is lacking: 1-2 is lower than 1-3 or 2-3 that many other units of this level have. Since this upgrade is required for wolf raiders, you will probably end up doing it, but 5 wood and 5 ore are better saved for a castle.
Wolf Rider
Wolf RiderHealth: 10Attack: 7Shots: noneMovement: ground
100 gold (9)Hex size: 2Defence: 5Dmg: 2-4Spd: 6 (swift)
Basically you're getting the same goblin, slightly better stats and larger size. Weak for level 2, wolf rider is only slightly better than level 1 centaur captain. Wolves should attack before attacked, applies to wolf raiders especially.
Wolf Raider
Wolf RaiderHealth: 10Attack: 8Shots: noneMovement: ground
140 gold (9)Hex size: 2Defence: 5Dmg: 3-4Spd: 8 (very swift)
Special: Attacks twice.
Awesome upgrade that makes wolves do about 2.5 times more damage. Defence and hit points remain the same, so use the sudden charge tactics. Try to get your target to waste their retaliation before raiders make their double move. Ahhh, HOMM1 memories... same two attacks, but those wolves were white and self-sufficient :) As for getting the upgrade - it is very expensive in terms of wood and ore because you are required to upgrade goblins first. If you're poor, you might even forget about using goblins and wolves in your main army, just let them stock up for a bad day.
OrcHealth: 15Attack: 8Shots: 12Movement: ground
150 gold (7)Hex size: 1Defence: 4Dmg: 2-5Spd: 4 (extra slow)
Weaker than beholders and elves, orcs are the weakest level 3 shooters, but that is also reflected in their low price. Reasonable stats, wide damage easily affected by bless and curse, slow speed which will be reflected on your hero movement, but if you plan using ogres in your army, they are just as slow, so feel free to take some orcs. Cyclops will replace orcs later on.
Orc Chieftain
Orc ChieftainHealth: 20Attack: 8Shots: 24Movement: ground
165 gold (7)Hex size: 1Defence: 4Dmg: 2-5Spd: 5 (slow)
A small and cheap upgrade that makes orcs slightly faster (same as ogre magi) and tougher. Do it if you want orcs to last longer or if all your ogres are upgraded already, so that the lowest army speed will be 5 instead of 4. Comparing the pictures, orc chieftain has one extra axe - this is to be interpreted as double amount of shots :)
OgreHealth: 40Attack: 13Shots: noneMovement: ground
300 gold (4)Hex size: 1Defence: 7Dmg: 6-12Spd: 4 (extra slow)
A great level 4 unit if it wasn't for the superlow speed. Nice damage, great attack, low price, while the low defence is backed up by plenty hit points. Orcs and ogres are a speed pair, so either have both or none for your main hero. Ogres make great defenders, bashing the enemy from close range as they approach your juicy shooters. For all ogres - watch out for curse and apply bless as required.
Ogre Magi
Ogre MagiHealth: 60Attack: 13Shots: noneMovement: ground
400 gold (4)Hex size: 1Defence: 7Dmg: 6-12Spd: 5 (slow)
Special: Can cast bloodlust spell on one ally per round at spell power 6, advanced level.
Great upgrade, 50% tougher for 33% extra price plus the spell bonus. Ogre magi are the toughest among their level, their supperiority undermined perhaps only by vampires' life drain. Stock up on these guys because they can dellay your enemy's victory by few thousand hit points. Ogre magi are still slow, but they don't just stand there anymore - bloodlust spell will assist the advancing armies while magi defend the shooters. Bloodlust increases attack skill for the time of 6 rounds.
RocHealth: 60Attack: 13Shots: noneMovement: flying
600 gold (3)Hex size: 2Defence: 11Dmg: 11-15Spd: 7 (extra swift)
Let's roc! A nice level 5 unit with higher hit points than most. Roc is also very balanced, having no weak sides such as damage range or low defence. Use them for whatever purpose, but being the only stronghold flyers they often die alone in the enemy crowd.
ThunderbirdHealth: 60Attack: 13Shots: noneMovement: flying
700 gold (3)Hex size: 2Defence: 11Dmg: 11-15Spd: 11 (quick)
Special: 20% chance for thunderbolt spell which does 10 damage per each thunderbird to target.
Thunderbolt strike is a useful damage since it is not affected by defence. The only flying unit for stronghold, they are still not good enough to fly over the castle walls alone. This upgrade is good to get the earlier spellcasting turn: speed 11 is the highest in stronghold, followed by 9 of ancient behemoth. And hey, the looks are good, they actually look more powerful to your human opponent.
CyclopsHealth: 70Attack: 15Shots: 16Movement: ground
750 gold (2)Hex size: 1Defence: 12Dmg: 16-20Spd: 6 (swift)
Special: can attack seige walls at basic ballistics level.
Now we're shooting! Only titan's lightning can hit stronger than cyclops' rocks, and that abbility to attack seige walls is completely exlusive to cyclops. Want 3 extra catapults? Split cyclops into multiple stacks, seige walls take same damage from 1 cyclops as from 100. Cyclops is also a well-balanced unit with no weakneses except for the hand-to-hand penalty. Keep that ammo cart handy for long ones.
Cyclops King
Cyclops KingHealth: 70Attack: 17Shots: 24Movement: ground
1100 gold (2)Hex size: 1Defence: 13Dmg: 16-20Spd: 8 (very swift)
Special: can attack seige walls at advanced ballistics level.
They aren't kings for nothing, packing two seige shots in one turn and leveling walls to the ground in no time. You'll notice that the lack of flyers is compensated by the cyclops' special abbilities. Kings however are quite pricey - look at that golden skirt armor that you are buying them for 350 gold! Attack, defence and speed improvements are too small to be worth 350 gold, so upgrade only if you are filthy rich and are heading for a long seige. Think about it, 2 kings cost almost as much as 3 normal cyclops!
BehemothHealth: 160Attack: 17Shots: noneMovement: ground
1500 gold (1)Hex size: 2Defence: 17Dmg: 30-50Spd: 6 (swift)
Special: target is able to use only 60% of its defence when attacked by behemoth.
That smile scares the hell out of whoever behemoth is attacking, reducing their abbility to defend themselves. Slow and quite vunerable, behemoth is also a cheap level 7 unit, definitely attack-oriented and able to deal huge damage by reducing enemy defence during the attack. Try to use charge tactics whenever possible, do not leave behemoth exposed to enemy attacks, too easy to lose them.
Ancient Behemoth
Ancient BehemothHealth: 300Attack: 19Shots: noneMovement: ground
3000g+1c (1)Hex size: 2Defence: 19Dmg: 30-50Spd: 9 (ultra swift)
Special: target is able to use only 20% of its defence when attacked by ancient behemoth.
Quite low on attack, defence and speed for the best creature, but hit points are at the top and the special abbility is amazing: the target is virtually defenceless however high it's skill is, even if it is commanded by a good hero, nothing helps, only 1/5th of defence will be useful to the scared enemy. Ancient behemoth is able to deal the highest damage amongst all level 7 units, but it's use is more strategic than that: always attack the unit with the highest defence skill since only behemoths can bypass it. If you are ever to face the ancient behemoth, command all your units to attack at once - its attack is great, but its defence is nothing special, making it a strategic target.