LONG post coming
Eagle: 2 turns, 2 strength, 20 moves, view 4, Anti Air power, cost 200, upkeep 2.
The 20 moves and 4 view lets the Eagle catch bats and other fliers. It will be 5 strength against other fliers so 3 of them have a good chance to kill a single Dragon. At 2 strength vs ground units it won't be overly useful to capture cities but it can bless to 3 easily due to good move rate or grouped with a Pegasi for even better combat stats. The cheap cost reflects the fact it's a specialized unit so it might get used/bought by players.
Crusader:
Not sure what to do with this guy. Pillagers idea of having him help in ruins makes sense.
He really looks like a hero to me, not a unit. So he just needs a portrait and you have a 4th hero ready to go. As a crusader hero he would be perfect for quests or getting extra XP from quests (and yes, the Paladin would have to become a Ranger)
Otherwise until you add designations for good/evil units he has no obvious function.
Mammoth: 4 turns, 8 strength, 14 moves, view 3, siege +3 power, cost 1400, upkeep 4, Snow move bonus - 2, +1 combat in snow.
I know you wanted to give group move power to units. But group move is meant to stack so that if 2 units each have +4 group move you get +8 move. Otherwise group move on heroes/items isn't very valuable. That makes giving group move to units dangerous because 5-6 of these guys would have a stack moving 30+ a turn.
So instead how about making this a +3 siege unit that players have asked for against cities/towers with L8 walls. Elephants/Mammoths have long been used to batter down gates and with his high strength he will probably live through the attack and be useable again on another city.
Scorpion: 2 turns, 4 strength, 12 moves, view 1, poison +4 power, cost 400, upkeep 2, Desert move bonus - 2, +2 combat in desert.
The poison power works as follows: At the start of battle, the poison numbers from all units (so 1 scorpion is 4, 2 is 8, 3 is 12 etc) in the stack is totaled. This number is multiplied by 4 to give a percentage of poisoning ALL enemy units (so 3 scorpions in a stack have 12 poison which gives 12x4=48% chance poison enemy units). The poison percentage is rolled for each unit individually rather than one roll for all enemy units. Poison reduces enemy strength by 2 (limited to 1, so a 1 strength unit that is poisoned suffers no effect).
The poison effect lasts BEYOND the battle if the enemy units survive. It cures at a rate of 1 strength per turn. So enemy units remain at -2 strength until that player starts his turn. At that point the poison drops to -1. On his following turn the units are back at full strength. Units that are blessed (strength) are immune to poison. Blessing units with poison cures it immediately and grants the +1 strength.
Ideally you would put 2 * on a poisoned unit to indicate there are 2 turns left. Then 1 * when there is 1 turn left etc. Helps players know how much longer they will remain poisoned.
As you can guess this is an excellent way to weaken enemy cities before assaulting them if you send in 6-7 scorpions to get to roughly 100% poison chance for all enemy units because you'll get all that turn with enemy units at -2 and all next turn with them at -1 before they are healed.
Now all you need is an equivalent unit with disease (remove 1 hit, lasts 1 turn)
Yeti: 2 turns, 4 strength, 14 moves, view 2, banding/horde/swarm +3 power, cost 600, upkeep 2, Snow move bonus - 2, +2 combat in snow.
Hard to find a unique power for this guy. Ones that the game needs (disease) don't apply to him. So for the moment all I can think of is to give him the swarm/horde/banding bonus like the Demon is getting. That keeps him roughly equivalent to the Hv Calv/Giant but not exactly the same.
Sand Worm: 3 turns, 6 strength, 14 moves, view 1, ignore walls power, cost 1000, upkeep 4, Desert move bonus - 1, +2 combat in desert.
I would make the move bonus groupable since you are waiting 3 turns to get one of these units so the least it can do is help you move better in the desert.
Kraken: 3 turns, 5 strength, 20 moves (4 on land), view 4, attack coastal cities power, cost 1000, upkeep 4. water move 1 all water types, 2 in swamp, +3 strength in water.
Sea Serpent: 1 turn, 2 strength, 20 moves (4 on land), view 3, attack coastal cities power, cost 250, upkeep 1, water move 1 all water types, 2 in swamp, +2 strength in water.
What are you envisioning these units doing now with the new boat types? Once you announced those new boats these units make a lot less sense to me. That's because on the warship you can now have land units fight at 6 (or was it 7 strength) strength so they can fight off these units easily.
The only power that makes sense for these units now is the ability to attack coastal cities from the water since they can move on both terrains. That gives them some actual real value as they are no longer going to be able to sink the better boat types. Note that the attack coastal cities power only applies to these units, not the rest of the stack (unless it's flying in which case a flying hero + Sea Serpents/Kraken becomes deadly to coastal cities).
Note: If you want to do something a bit more radical you could add the Disease skill (exactly the same as poison except it removes 1 hit and only lasts 1 turn). Give the Medusa a +4 Disease skill, change her to a 2 turn 5 strength unit, give her a +1 combat bonus in ruin terrain and lower her cost/upkeep to the scorpion's numbers. Then make the Mammoth the unit with the -1 stack bonus (fits with the Elephant getting the +2 stack bonus in open), and change him to 3 turns, 7 strength and make him the ally instead of the Medusa.
KGB