Jeffr both me and Machaka attacked you because Ironhawk told us how scary you are.
Machaka attacked you because he tried to help Man and i attacked you because i knew your playstyle and assumed that if i do not attack you you will attack me soon anyways. I thought that my jaguar warriors are stronger
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Regarding the soul stone: It gives you 1 free summoning of call of the wilds per turn.
According the Ghost riders: They are a cheesy strat. Zen made them D6 to cast (Vanilla D4) so they are not as frequent anymore but still annoying. In vanilla i always summoned a bunch of demiliches just for the purpose of Ghost Rider Summoning and as "Landsturm".
Some kind of SCs beat the ghost riders and so do very large and well composed armies. But Ghost Riders are a problem since they are so cost effective. Even if your Army is huge and basically untouchable some Ghost Riders cast upon them can force this army to spend all their gems and thus soften it up for the next combat. It is almost impossible though to do several such Armies that cannot be damaged by Ghost Riders. They are just a great great tool.
With Ashen Angel + Ghost Rider attacks you can soften up almost any Army/SC. But they are fairly late spells so they deserve to be powerful.