the.com/poisoned chalice

means Something that looks like a prize or privilege but ends up harming whoever accepts it — often a job or role that seems desirable yet carries hidden costs.

from From the literal poisoned cup of murder lore and stagecraft — most famously evoked in Shakespeare's Macbeth, where Macbeth fears that violence, once taught, returns 'to plague th' inventor' like a poisoned chalice handed back to the one who prepared it. The phrase moved from theater and literature into general use in the 20th century, especially in politics and business, to describe appointments or deals that seem like honors but turn out to be traps.