A 10k general exp is an item in Evony TKR (The King's Return). It can be found after killing certain monsters or bosses, with some of them listed below.
The description of 10K General EXP in Evony TKR says:
Grants your General 10,000 General EXP.
10K General EXP is known to drop from a number of bosses or monsters upon killing, including Behemoth, Phoenix, Jormungandr and Typhon.
Note: This list may be incomplete.