For the advanced orc priests of the Orc Empire, it didn't matter how many orcs Abel killed on the orc battlefield. He could deter the Orc Empire's invasion plan in however ways he wished, and it wouldn't affect them in any direct way.
The advanced orc priests could live very long. They had plenty of time to wait for the Orc Empire to rise again. In fact, having many dead orcs could help ease the problem of the lack of produce. Even if most of them didn't die immediately, the mass starvation would still take their lives away.
Still, Abel destroyed sacred relics. That was something that they couldn't tolerate. It was an act that threatened their core interests, and they were willing to go at any length to lure him to come to the Orc Empire. It was a desperate measure, honestly speaking. With the Budapest Mountain as somewhat of an exception, the advanced priests would always be detected if they tried to step on human territories.