You can perform any action you choose (assuming the timing is correct for it - for instance, you can't use activated powers if they haven't been in your party since the beginning of your most recent turn). You can use payment powers, competion powers, activated powers, instant abilities, etc. It does not matter what effect started the chain, you can add any effect to the chain that you wish to use at the time.
Activated powers, abilities, and combat are the only things that have restrictions on them. I already gave you the restriction on activated powers. Abilities and combat can only be used during your action phase when the chain is empty and you have priority.
Hope this helps!
WoW TCG Judge LV2
Player Managment 2
WoW TCG RK2
Disclaimer: All answers provided assume that you have enough resources to exhaust, and are able to pay any other additional costs, in order to play the referenced allies/powers/abilities.